Slade Wilson (Earth-4678)

Slade Wilson, also known by his alias Deathstroke, was a soldier in the U.S. Army during the Vietnam War, who took part of an experimental super-soldier program that attempted to recreate the feat of Captain America, where he gained enhanced strength, agility, healing factor and intelligence. Deathstroke became a mercenary soon after the experiment and rapidly gained a reputation as one of the world's greatest assassins. Following his defeat and incarceration at the hands of Batman, Deathstroke escaped from the maximum security wing of Blackgate Prison and worked as an ally of Scarecrow and the Arkham Knight.

Source

 * https://arkhamcity.fandom.com/wiki/Deathstroke