Not Arnold's Terminator

Marv Wolfman and George Perez created Slade Wilson, Deathstroke the Terminator, 4 years before the James Cameron's film the Terminator. Originally an antagonist for the Teen Titans, Deathstroke has grown into a credible threat to Batman, the Green Arrow, and others.

As a mercenary and assassin, Deathstroke's motivation is always tied to someone else's bank account. He operates in a similar fashion as Killer Moth was probably meant to function. Deathstroke's motivations revolve around money, but he also forms grudges against Dick Grayson (Robin/Nightwing), Green Arrow, and Batman. All three of these heroes frequently get the better of him.

Originally, Deathstroke came off as pretty creepy, and kind of lame. A middle-aged mercenary who teams up with a teenage girl (Terra) to infiltrate and destroy a team of teenage superheroes (Teen Titans) seems as cringey as it is pathetic. Certainly a dude that stoops to fighting underage heroes cant possibly be a serious threat to Batman. After this first arc, Deathstroke turns into an anti-hero of sorts. His children become members of the Teen Titans, and most of his early arcs revolve around family issues.

Later his services are bought by Dr. Light, Lex Luthor, the Injustice League, the Secret Society of Supervillains, and Talia al Ghul's League of Assassins, and even the Crime Syndicate. With each rebooted continuity, Deathstroke becomes a more dangerous, more credible villain, and is distanced further from his original weird Teen Titans relationship.

Deathstroke recently has become a more visible antagonist. He is the main villain in season 3 of the Arrow television show, makes a cameo at the end of the 2017 Justice League film, and makes several appearances in DC's animated films. He is also an important villain in Arkham Origins and in Arkham Knight.