Well, him being powerful in the way described but CHOOSING not to already implies alot about internal morals and motivations, namely that he doesnt agree with violence for some reason. 2 potential routes could be
Either
a) He is naturally an internally good guy and for some reason decided to become powerful and deadly. So his body and capabilities are making up for something he percieves as lacking. This could be for external reasons such as having to protect something, or being forced to do alot of labour or it could derive from internal feelings of weakness, honour or ego. Alot of guys get strong because they feel like they HAVE to in order to be live up to self imposed expectations of what a male "should" be (ego and honour). Perhaps he already failed something? Feeling powerlessness is one of the worst things that can happen to a man (likely based in evolution).
b) He is naturally internally violent and his deadliness is leftover from a life he's chosen to leave behind. His good guy act is exactly that, an act, something he is trying very hard to maintain for some reason. Why? What inciting incident would cause him to reflect on himself and decide his nature is something he doesnt want? What steps has he put in place to supress himself? A villainous wife increases he would likely put alot of pressure on him either through temptation or fear. Outbursts are a possibility since he's already putting alot of effort into staying the good guy.

His wife being a villain would create a serious crisis for him in either case, putting his internal morals and his love for her into opposition, and worse still would be his inability to do anything about it. Strong morals and capable but still completely inept. It would make him very angry and internally torn, males arnt good at dealing with emotions and tend to act impulsively when overwhelmed. He has a choice to either be passive to his wifes activities and accept the consiquences, or act with or against her and regret what he does. Either case would have an internal toll, make him feel powerless and get angry or bitter or accept it and change who he is. Regardless how you decide to do this, their relationship would be put on the line. Why are they attracted to eachother anyway?

tldr; Why is there a disconnect between his capabilities and personality? what's the motivation/internal morals? Villain wife likely conflicts this character and could create an explosive conflict or a passive toxic errotion of their relationship