Overkill is a vigilante with hands and eyes made of metal. Described by a City cop as a "robo-ninja", he believes that violence is always the best solution to a problem. His past is a mystery, but it is known that he was once an agent for the organization called AEGIS until he somehow finally snapped mentally, and 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, who he also believes is still alive.
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.