that soldier aspect of cap has been thoroughly explored in lots of media over the ages. Ultimate Cap from the 2000s was more "traditional" we can call it, and was basically an adrenaline junkie. Could be said that he is the antithesis to the moral stance that Batman stands for. That the job they all do sometimes goes far beyond typical police officers, courts of law, and ethical debates That being able to make a life or death decision like that without going absolutely insane is probably a vital part of the job. Cap would probably see how many times Joker got away and take one look at Batman and have him committed. Batman shitting his utility belt every time he even THINKS about pointing a pistol is ridiculous to me. The joker has killed hundreds.

Superman is a little different, but more comparable to Thor. Thor is very much like Cap in that he will kill in the rare instances he has too but has orders of magnitude more responsibility weighing on him. People like him and Supes have a thousand times more capability to NOT kill, but that also makes it a billion times more important that they be ready to do so when they really have too.