Anyway I think the dark prince/Duke is probably the best because going unhinged in a castle is more fun than in an alleyway or your local veterans club. The street kid and traumatized soldier feels a bit stereotypical and probably a bit stigmatising. Like if a dude gets traumatized or is poor he shouldn't be treated like an animal, there could be some commentary on how society treats veterans and the impoverished but if you wanna have some fun with a dude going crazy and another character being horny about it then some Ritch guy in a tower is probably better.
However one could say that you'd then be romanticizing power dynamics, which I'd say isn't that bad if it's a prince, but worth bearing in mind, not sure what the difference between a Duke and a prince is given the two choices having basically the same premise of "powerful guy with familial expectations has probably done a murder".
I think that just a regular person, like a baker or a lawyer, whose secretly brimming with primal rage could be interesting. Someone who has a steady job and one or two friends but is filled with an anger that they have to unleash. I think I'd find that relatable, given the way things are currently.