Stan Kovacs (Earth-90: Pre-Crisis)

"Whatever it is... It's either a cop or is working for them!"

- Stan about "The Flash"

Stan Kovacs was the criminal mastermind behind the Museum theft in Central City.

Early Life
At some point, Stan became a known criminal to the point where the police database has a record of him working with other known criminal such as Kate Tatting or Parry Johnson.

At some point, he met and fell in love with Central City Museum Pr Celia Wayne. He eventually convinced her to betray the museum and planned with her to steal the Death Mask of Rasputin.

The Museum theft
In 1990, he invited a crew to the Marco's Billiards to prepare a plan for robbing the Museum at Central City. On this way to the city, his car was intercepted by the police, and he and his allies had no other choice but to kill them all. Later, when they tried to rob Star Labs for material, he deduced that Darrell Hennings was attacked and asked Franco Mortelli to drive out of the place. They were chased by a red figure who managed to blind the Mortelli which caused an accident that killed him. He woke up from the crashed car and escape with Kate who already got what they needed for the robbery. Later, in his apartment, the team discussed what happened and Stan revealed that he checked who called the police and deduced that "The Flash" was at least working for them. When Mark Bernhardt tried to quit, Stan made him a final offer. Stan killed him and left his corpse with a bomb at Marco's Billiards after sending a message to the police for the Flash to meet him up there. Stan later watched on TV the situation at the bar where he saw the Flash present. He detonated the bomb and believed to have killed the Flash before making out with Celia who was at his apartment. Later, Celia called about the fact that the police is aware about his involvement and that the mask is about to be moved. Stan decided to make the crew attack different part of the city in order to distract the police while he and Celia stole the mask. During the operation, the Flash showed up after stopping the crime wave and fought him until he is pinned to the ground. He was later arrested along with Celia.

Trivia

 * From all the villains on the show, he was the one who came the closest to discover the Flash's identity as he has figured out that he worked for the police.