Overkill is a vigilante with cybernetic hands and eyes. Described by a City cop as a "robo-ninja", Overkill believes violence is always the best solution to any problem. His past is a mystery, but it is known that he was once an agent for the organization AEGIS until he somehow finally snapped mentally and went rogue; he admitted to having a social media account under the pseudonym GunSkull17, also looking at Arthur Everest's Reddit thread regarding the conspiracies about The Terror's survival. These days, he has a vendetta against The Terror himself, whom he also believes is still alive.
Before he became Overkill, he was once Uncle Samson's sidekick Straight Shooter and was traumatized from losing his team, eyes and hands.
It has been suggested that he was a former love interest for Miss Lint.
Overkill is your typical masked gun-toting vigilante who punishes evildoers wherever he goes. However, his dark attitude frequently clashes with the more noble seeker of justice The Tick, and as a result, they often jab at each other. Like Arthur, he is implied to have an extreme version of obsessive-compulsive disorder (OCD) as seen in his fervent search for proof that The Terror lived through his last battle with Superian.