Hush (Arrowverse)

Thomas "Tommy" Elliot is the childhood ex-best friend-turned-enemy of Bruce Wayne

Early Years
Tommy was childhood friends with Bruce Wayne. In 2005, his parents got in a car accident, killing his dad, but his mom was saved by Batman.

Return to Gotham
In 2018, Tommy returned to Gotham, believing Bruce returned, reliving to Kate at a party that he knows Bruce is Batman and has planted bombs on three elevators, blowing up one of them. He is eventually stopped by Kate as Batwoman and Alice, where is sent to Arkham Asylum.

Personality
Tommy is extremely arrogant, snobby, and mentally unstable to the point of lacking any form of logic; as he holds a grudge against Bruce Wayne (under the persona of Batman) for saving his mother's life, which prevented him from getting his inheritance, he also states that Batman ruined his life.

Reagan described him by saying he's, "dangerous, hazardous waste. Thinks he's doing us all a favor when he really just helps fund the laws that are separating our city".