So my thinking was that this guy almost had the captain America treatment in the 1940s, was aware of his powers embraced them and joined the fight. Volunteered for the program that put the metal into onto his skeleton. Was a hero for a long time, but over the years became more and more jaded which led him to be coming more and more violent until about 5-10 years ago (still working out the time line) he decided to retire. Hasn’t popped his claws since.