587. Sharp

599. Ms. Sinclair's mother

Here's the cleaned up clues list.

481. Original; high school student when last seen; close friend of cast character during teen years J**IE
487. Original; unrevealed; villager in an African nation  F*YIN**LA
511. Comics; CEO; The Power Company; had nannite-created powers BI*MAX /  JACK *P*EER
522. Original; nation's President; gave a speech on a late hero **AW
541. Original; government agent; electrocuted underwater ALEX *C*TT
546. Original; slave; whipped for accidentally burning cloth prior to being freed by heroes MAR* [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPRTVWXZ2345780]
554. Original; government agent; hunted a villain who killed him T**NG
569. Original; drug dealer; sold drag that turned people into rage monsters KE*IN **GGIN*
578. Original; pastor; lived in Odessa, Texas in 1925 P*WELL * [LOCKED; characters found at time of locking: BCEFGIJKLPTVW2780]
603. Comics; unrevealed; Batman: Shadow of the Bat; born with mental illness and prone to attacking others AMYGDALA /  AAR*N *ELZINGER
604. Comics (gender swapped, so slightly different real name); criminal; The Flash; can induce vertigo T*P / R**A DILL*N
608. Comics (likely different real name, Arrowverse version missing first word in code name); criminal, weapons dealer; The Flash; can create box-like force fields BL*CK / VANE**A JAN*EN
609. Original; scientist; alien with thorns on his forearms R**AN V**E
610. Comics; serial killer; The Fox and the Crow (real name), Green Arrow (code name); obsessed with main character's earliest vigilante persona *TAR CITY  *LAYER a.k.a.  INMATE ##22 /  *TANLEY  D*VER
613. Comics; assassin, CEO; Young Justice; created an enormous destructive tidal wave RIP R*AR /  R***ELL  R*GER*
614. Original; newswoman; interviewed counsellor on anti-vigilantism bill JANE W**D*
616. Comics; vigilante; Batwoman, but inspired by character from Detective Comics; only seen in a photo KATE KANE (EART*-##) [For this one I'm locking the numbers as this one's now too easy to guess otherwise]
623. Original, though name might be a nod to two real life people; business founder, investment magnate, philanthropist, socialite; held a fundraising gala where she spokie with cast characters looking for her son T*ERE*A MERKEL
624. Original; unrevealed, likely student; cast character's first cousin once removed C*RI*
625. Comics; nuclear truck driver; The Flash: Iron Heights; has power to emit dangerous levels of radiation FALL**T / NEIL B*RMAN
626. Original; crime lord (code name refers to another occupation that he doesn't actually have); took over part of town after an earthquake T*E MAY*R /  XAVIER REED
628. Original; cultist; part of a coven wishing for old deities to be worshipped FEI*A [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]
631. Comics (indirectly); posed as chief of police; The Flash Secret Files and Origins; replaced main version of the character DAVID *ING* (MIRR*RVER*E)
636. Comics (comics version's first name unrevealed); technology firm employee; The Flash; fired from organization and then killed for being whistleblower GENE ***KK
637. Original; arms dealer; came to town to sell a shipment of stolen weapons but was interrupted by cast character LE* M*ELLER
639. Comics (indirectly); timeline protector; Hellblazer; mistakenly believed herself to be the real version A*TRA L*G*E (R*B*T)
643. Original; bus driver, criminal; stomach slashed by major villain KEI**A M**RE
646. Original; unrevealed; gained powers in an experiment JA*PER T*WNE*
647. Original; criminal; right-hand man for recurring villain **ECK
648. Comics (prototype from magazine); vigilante; Action Comics  (prototype from Science Fiction: The Advance Guard of Future Civilization); villainous counterpart of a superhero **PERMAN / KAL-EL (EART*- T*D22)
651. Original; councilman; ally of major villain K*LLEN*
655. Original, but resembles character based on comics; mobster; resembles character from Justice League of America; seen in artificial reality C*TTER M*RAN
656. Original; doctor; assigned to care for main character RAFAEL R*DRIG*EZ
657. Original; police officer; provided superhero with intel AN**N
662. Comics; drug dealer; Green Arrow and Black Canary; attempted to murder a police detective *EAN **N**
664. Comics (different real surname); student; Flashpoint; had the power to harness electrical energy BLACK**T / FAR**Q GIBRAN
666. Original; named after real person but not a true counterpart; criminal; kidnapped major character's son J**N BYRNE
667. Real person; astronaut; major villain impersonated him J**N *WIGERT
670. Original; anchorwoman; often reports on main character's activities *ANA *EWITT [LOCKED; both remaining letters the same; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]
671. Comics; criminal, orphanage head; All-American Comics; test subject for major villain CYR** G*LD
674. Original; unrevealed; sibling of major villain *RLIN DWYER'* *I*TER
676. Original; criminal; robbed blood banks for sustenance *ILA* W*ITE
677. Comics; astronomer, assassin; Crisis on Infinite Earths; may have replaced another character with the same code name due to the Arrowverse Crisis DR. LIG*T /  KIMIY* ****I
681. Comics; newspaper intern turned police detective; Showcase; mistook main character for her husband IRI* WE*T-ALLEN (EART*-2)
683. Original; unrevealed; fan of major character's writing D*RI*
687. Folklore; probably none; folklore of the Americas; fugitive from evil realm C**PACABRA
688. Original; unrevealed; accused of being a witch JANE *AWT**RNE
689. Original; music student graduate; attended University of Cincinnati VANITA RIP**N
696. Original; night club owner; main character slept with his fiancée MAX F*LLER [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ2345780]
706. Original; singer; participated in reality TV competition *A*CÉY
708. Original; football player running back; testified against murderous brother AP*LL* TE*L**
710. Original; scientist; wife of someone who was impersonated for a long time TE** M*RGAN
712. Original; unrevealed; was seen as candidate for human trials DERRICK *IMM*N*
713. Original; director; worked for major studio in 1937 ARN*LD C*LE**N
714. Original; police officer; killed in an ambush J*NE*
716. Comics (indirectly); science based employee to the extent applicable; Action Comics; counterpart of recurring character ALEX DANVER*' FAT*ER (*B*IDIAN PLATIN*M)
717. Original; scientist; ally of main character's mother JET*RIAN IND**TRIE* *EMAT*L*GI*T (note: while not named in the show souce sources claim she's DR. T*VA; I'll accept either name)
718. Original; unrevealed; version of another character, attended a World's Fair EDIT* B*ARDMAN
723. Original; federal agent; killed by cultists DEM**
729. Similar to comics character with different code name and real name; doctor turned criminal; Wonder Woman;  augmented herself using stolen technology  CYBER-W*MAN /  LA*RA  WA**INGT*N

 

It's been a day since any guesses. I can add another letter but it will cost 25 bonus shots for the next letter down the pipeline or 40 if you want to pick a specific letter (which could potentially be the next letter anyway).

Adding the shows they're from; I don't think anyone left has appeared in multiple shows but if they have, only the main one noted.

Letters/numbers found so far: ABCDEFGIJKLMNPQTVWXYZ12345780

481. Original; high school student when last seen; close friend of cast character during teen years J**IE; Supergirl
487. Original; unrevealed; villager in an African nation  F*YIN**LA; DC's Legends of Tomorrow
511. Comics; CEO; The Power Company; had nannite-created powers BI*MAX /  JACK *P*EER; Supergirl
522. Original; nation's President; gave a speech on a late hero **AW; DC's Legends of Tomorrow
541. Original; government agent; electrocuted underwater ALEX *C*TT; Arrow
546. Original; slave; whipped for accidentally burning cloth prior to being freed by heroes MAR* [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPRTVWXZ2345780]; DC's Legends of Tomorrow
554. Original; government agent; hunted a villain who killed him T**NG; Supergirl
569. Original; drug dealer; sold drag that turned people into rage monsters KE*IN **GGIN*; Supergirl
578. Original; pastor; lived in Odessa, Texas in 1925 P**ELL * [LOCKED; characters found at time of locking: BCEFGIJKLPTVW2780]; DC's Legends of Tomorrow
603. Comics; unrevealed; Batman: Shadow of the Bat; born with mental illness and prone to attacking others AMYGDALA /  AAR*N *ELZINGER; Batwoman
604. Comics (gender swapped, so slightly different real name); criminal; The Flash; can induce vertigo T*P / R**A DILL*N; The Flash
608. Comics (likely different real name, Arrowverse version missing first word in code name); criminal, weapons dealer; The Flash; can create box-like force fields BL*CK / VANE**A JAN*EN; The Flash
609. Original; scientist; alien with thorns on his forearms R**AN V**E; Supergirl
610. Comics; serial killer; The Fox and the Crow (real name), Green Arrow (code name); obsessed with main character's earliest vigilante persona *TAR CITY  *LAYER a.k.a.  INMATE ##22 /  *TANLEY  D*VER; Arrow
613. Comics; assassin, CEO; Young Justice; created an enormous destructive tidal wave RIP R*AR /  R***ELL  R*GER*; Supergirl
614. Original; newswoman; interviewed counsellor on anti-vigilantism bill JANE W**D*; Arrow
616. Comics; vigilante; Batwoman, but inspired by character from Detective Comics; only seen in a photo KATE KANE (EART*-##) [For this one I'm locking the numbers as this one's now too easy to guess otherwise; both digits the same]; Batwoman
623. Original, though name might be a nod to two real life people; business founder, investment magnate, philanthropist, socialite; held a fundraising gala where she spokie with cast characters looking for her son T*ERE*A MERKEL; the Flash
624. Original; unrevealed, likely student; cast character's first cousin once removed C*RI*; DC's Legends of Tomorrow
625. Comics; nuclear truck driver; The Flash: Iron Heights; has power to emit dangerous levels of radiation FALL**T / NEIL B*RMAN; The Flash
626. Original; crime lord (code name refers to another occupation that he doesn't actually have); took over part of town after an earthquake T*E MAY*R /  XAVIER REED; Arrow
628. Original; cultist; part of a coven wishing for old deities to be worshipped FEI*A [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]; Supergirl
631. Comics (indirectly); posed as chief of police; The Flash Secret Files and Origins; replaced main version of the character DAVID *ING* (MIRR*RVER*E); the Flash
636. Comics (comics version's first name unrevealed); technology firm employee; The Flash; fired from organization and then killed for being whistleblower GENE ***KK; The Flash
637. Original; arms dealer; came to town to sell a shipment of stolen weapons but was interrupted by cast character LE* M*ELLER; Arrow
639. Comics (indirectly); timeline protector; Hellblazer; mistakenly believed herself to be the real version A*TRA L*G*E (R*B*T); DC's Legends of Tomorrow
643. Original; bus driver, criminal; stomach slashed by major villain KEI**A M**RE; The Flash
646. Original; unrevealed; gained powers in an experiment JA*PER T*WNE*; Superman and Lois
647. Original; criminal; right-hand man for recurring villain **ECK; Arrow
648. Comics (prototype from magazine); vigilante; Action Comics  (prototype from Science Fiction: The Advance Guard of Future Civilization); villainous counterpart of a superhero **PERMAN / KAL-EL (EART*- T*D22); Superman and Lois
651. Original; councilman; ally of major villain K*LLEN*; Arrow
655. Original, but resembles character based on comics; mobster; resembles character from Justice League of America; seen in artificial reality C*TTER M*RAN; The Flash
656. Original; doctor; assigned to care for main character RAFAEL R*DRIG*EZ; Batwoman
657. Original; police officer; provided superhero with intel AN**N; Arrow
662. Comics; drug dealer; Green Arrow and Black Canary; attempted to murder a police detective *EAN **N**; Arrow
664. Comics (different real surname); student; Flashpoint; had the power to harness electrical energy BLACK**T / FAR**Q GIBRAN; The Flash
666. Original; named after real person but not a true counterpart; criminal; kidnapped major character's son J**N BYRNE; Arrow
667. Real person; astronaut; major villain impersonated him J**N *WIGERT; Arrow
670. Original; anchorwoman; often reports on main character's activities *ANA *EWITT [LOCKED; both remaining letters the same; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]; Batwoman
671. Comics; criminal, orphanage head; All-American Comics; test subject for major villain CYR** G*LD; Arrow
674. Original; unrevealed; sibling of major villain *RLIN DWYER'* *I*TER; The Flash
676. Original; criminal; robbed blood banks for sustenance *ILA* W*ITE; Supergirl
677. Comics; astronomer, assassin; Crisis on Infinite Earths; may have replaced another character with the same code name due to the Arrowverse Crisis DR. LIG*T /  KIMIY* ****I; The Flash
681. Comics; newspaper intern turned police detective; Showcase; mistook main character for her husband IRI* WE*T-ALLEN (EART*-2); The Flash
683. Original; unrevealed; fan of major character's writing D*RI*; DC's Legends of Tomorrow
687. Folklore; probably none; folklore of the Americas; fugitive from evil realm C**PACABRA; DC's Legends of Tomorrow
688. Original; unrevealed; accused of being a witch JANE *AWT**RNE; DC's Legends of Tomorrow
689. Original; music student graduate; attended University of Cincinnati VANITA RIP**N;
Supergirl
696. Original; night club owner; main character slept with his fiancée MAX F*LLER [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ2345780]; Arrow
706. Original; singer; participated in reality TV competition *A*CÉY; DC's Legends of Tomorrow
708. Original; football player running back; testified against murderous brother AP*LL* TE*L**; Supergirl
710. Original; scientist; wife of someone who was impersonated for a long time TE** M*RGAN; The Flash
712. Original; unrevealed; was seen as candidate for human trials DERRICK *IMM*N*; Supergirl
713. Original; director; worked for major studio in 1937 ARN*LD C*LE**N; DC's Legends of Tomorrow
714. Original; police officer; killed in an ambush J*NE*; Arrow
716. Comics (indirectly); science based employee to the extent applicable; Action Comics; counterpart of recurring character ALEX DANVER*' FAT*ER (*B*IDIAN PLATIN*M); Supergirl
717. Original; scientist; ally of main character's mother JET*RIAN IND**TRIE* *EMAT*L*GI*T (note: while not named in the show souce sources claim she's DR. T*VA; I'll accept either name); Batwoman
718. Original; unrevealed; version of another character, attended a World's Fair EDIT* B*ARDMAN; DC's Legends of Tomorrow
723. Original; federal agent; killed by cultists DEM**; Supergirl
729. Similar to comics character with different code name and real name; doctor turned criminal; Wonder Woman;  augmented herself using stolen technology  CYBER-W*MAN /  LA*RA  WA**INGT*N; Arrow

 

603. Amygdala/Aaron Helzinger

608. Block/Vanessa Jansen

613. Rip Roar/Russell Rogers

616. Kate Kane (Earth-99)

625. Fallout/Neil Borman

636. Gene Huskk

646. Jasper Townes

Those are correct; list updated. The comic vesion of the Top was the first major Flash/Barry Allen foe to be dead for a long period of time. Star City Slayer is very loosely based on Stanley from the humour series Stanley and His Monster. Earth-99's Kate Kane was only seen in a photo and was killed by that Earth's rogue Bruce Wayne. The "real" Arrowvese Astra Logue first appeared in Constantine. The rogue Superman killed Natalie Irons' mom.

 

Pruning the dead clues:

Letters/numbers found so far: ABCDEFGIJKLMNPQTVWXYZ12345780

481. Original; high school student when last seen; close friend of cast character during teen years J**IE; Supergirl
487. Original; unrevealed; villager in an African nation  F*YIN**LA; DC's Legends of Tomorrow
511. Comics; CEO; The Power Company; had nannite-created powers BI*MAX /  JACK *P*EER; Supergirl
522. Original; nation's President; gave a speech on a late hero **AW; DC's Legends of Tomorrow
541. Original; government agent; electrocuted underwater ALEX *C*TT; Arrow
546. Original; slave; whipped for accidentally burning cloth prior to being freed by heroes MAR* [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPRTVWXZ2345780]; DC's Legends of Tomorrow
554. Original; government agent; hunted a villain who killed him T**NG; Supergirl
569. Original; drug dealer; sold drag that turned people into rage monsters KE*IN **GGIN*; Supergirl
578. Original; pastor; lived in Odessa, Texas in 1925 P**ELL * [LOCKED; characters found at time of locking: BCEFGIJKLPTVW2780]; DC's Legends of Tomorrow
609. Original; scientist; alien with thorns on his forearms R**AN V**E; Supergirl
624. Original; unrevealed, likely student; cast character's first cousin once removed C*RI*; DC's Legends of Tomorrow
628. Original; cultist; part of a coven wishing for old deities to be worshipped FEI*A [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]; Supergirl
631. Comics (indirectly); posed as chief of police; The Flash Secret Files and Origins; replaced main version of the character DAVID *ING* (MIRR*RVER*E); the Flash
637. Original; arms dealer; came to town to sell a shipment of stolen weapons but was interrupted by cast character LE* M*ELLER; Arrow
643. Original; bus driver, criminal; stomach slashed by major villain KEI**A M**RE; The Flash
647. Original; criminal; right-hand man for recurring villain **ECK; Arrow
651. Original; councilman; ally of major villain K*LLEN*; Arrow
655. Original, but resembles character based on comics; mobster; resembles character from Justice League of America; seen in artificial reality C*TTER M*RAN; The Flash
656. Original; doctor; assigned to care for main character RAFAEL R*DRIG*EZ; Batwoman
657. Original; police officer; provided superhero with intel AN**N; Arrow
662. Comics; drug dealer; Green Arrow and Black Canary; attempted to murder a police detective *EAN **N**; Arrow
664. Comics (different real surname); student; Flashpoint; had the power to harness electrical energy BLACK**T / FAR**Q GIBRAN; The Flash
666. Original; named after real person but not a true counterpart; criminal; kidnapped major character's son J**N BYRNE; Arrow
667. Real person; astronaut; major villain impersonated him J**N *WIGERT; Arrow
670. Original; anchorwoman; often reports on main character's activities *ANA *EWITT [LOCKED; both remaining letters the same; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ245780]; Batwoman
671. Comics; criminal, orphanage head; All-American Comics; test subject for major villain CYR** G*LD; Arrow
674. Original; unrevealed; sibling of major villain *RLIN DWYER'* *I*TER; The Flash
676. Original; criminal; robbed blood banks for sustenance *ILA* W*ITE; Supergirl
677. Comics; astronomer, assassin; Crisis on Infinite Earths; may have replaced another character with the same code name due to the Arrowverse Crisis DR. LIG*T /  KIMIY* ****I; The Flash
681. Comics; newspaper intern turned police detective; Showcase; mistook main character for her husband IRI* WE*T-ALLEN (EART*-2); The Flash
683. Original; unrevealed; fan of major character's writing D*RI*; DC's Legends of Tomorrow
687. Folklore; probably none; folklore of the Americas; fugitive from evil realm C**PACABRA; DC's Legends of Tomorrow
688. Original; unrevealed; accused of being a witch JANE *AWT**RNE; DC's Legends of Tomorrow
689. Original; music student graduate; attended University of Cincinnati VANITA RIP**N;
Supergirl
696. Original; night club owner; main character slept with his fiancée MAX F*LLER [LOCKED; characters found at time of locking: ABCDEFGIJKLMNPTVWXZ2345780]; Arrow
706. Original; singer; participated in reality TV competition *A*CÉY; DC's Legends of Tomorrow
708. Original; football player running back; testified against murderous brother AP*LL* TE*L**; Supergirl
710. Original; scientist; wife of someone who was impersonated for a long time TE** M*RGAN; The Flash
712. Original; unrevealed; was seen as candidate for human trials DERRICK *IMM*N*; Supergirl
713. Original; director; worked for major studio in 1937 ARN*LD C*LE**N; DC's Legends of Tomorrow
714. Original; police officer; killed in an ambush J*NE*; Arrow
716. Comics (indirectly); science based employee to the extent applicable; Action Comics; counterpart of recurring character ALEX DANVER*' FAT*ER (*B*IDIAN PLATIN*M); Supergirl
717. Original; scientist; ally of main character's mother JET*RIAN IND**TRIE* *EMAT*L*GI*T (note: while not named in the show souce sources claim she's DR. T*VA; I'll accept either name); Batwoman
718. Original; unrevealed; version of another character, attended a World's Fair EDIT* B*ARDMAN; DC's Legends of Tomorrow
723. Original; federal agent; killed by cultists DEM**; Supergirl
729. Similar to comics character with different code name and real name; doctor turned criminal; Wonder Woman;  augmented herself using stolen technology  CYBER-W*MAN /  LA*RA  WA**INGT*N; Arrow

 

487 Foyinsola