An electronics expert and convicted thief steals a super-hero’s costume to save his daughter’s life. He goes on to become a super-hero in that same costume. Who is he?

Scott Lang is the second Ant-Man, and his origin matches this description. He was an electronics expert and convicted thief who stole the Ant-Man costume (from Hank Pym) to save his daughter's life (she had a serious heart condition). He then became a superhero using the costume, eventually redeeming himself and joining the Avengers. Tony Stark is Iron Man, Roger Bochs is Box, and Henry Pym is the original Ant-Man.