Deathstroke

Background
U.S. Army officer Slade Wilson volunteered for dangerous hormone experiments designed to create super soldiers. His strength, agility, stamina and brain capacity increased, Slade became a mercenary following the end of his army career and sold his services to the highest bidder as one of, if not the best, mercenary in the world.

Alternate Future
In the alternate timeline where the conflict between heroes and villains has escalated to war, Deathstoke has joined forces alongside Lex Luthor in fighting the remnants of the Justice League.

While initially confronting and attacking Wonder Woman during the final battle, he steals her lasso and uses it on Batman, trapping him and attempting to beat him to death save for the intervention of the Joker, who, in a fit over who should kill Batman, fired a bazooka at them both.

While surviving the blast relatively unscathed, Deathstroke defended himself against Brainiac's invading armies before being digitized alongside Cyborg, Wildcat, Killer Croc, and Circe.

Involvement

 * Deathstroke is an iconic villain who appears at various locations in Metropolis as part of the More Than You Can Chew and Fanboy feats. If a hero encounters him he will knock them back and then leave, if a villain encounters him he will make a comment and then disappear.

Heroes

 * Deathstroke is also in a mission by Oracle or Batman where the Riddler (now retired) has been a hit by Joker and Joker hired Deathstroke to kill the Riddler. You fight Deathstroke and you must beat him to win.
 * Deathstroke is also a boss in the lighthouse duo he will fight along killer croc when you meet up with Nightwing.

Villains

 * Deathstroke is in the Smallville alert if you're a villain. At the end of the Smallville Alert where you fight Doomsday, The Secret Society of Super-Villains sends you help in the form of Bizarro, Solomon Grundy, Killer Frost, and Deathstroke the awesomeness. They help you fight him and do damage they can revive you and you can revive them.

Trivia

 * Deathstroke first appeared in The New Teen Titans #2
 * Deathstroke is voiced by Patrick Seitz