Even if you cannot be a Njerpz by culture, eat human flesh while not starving and take someone's possessions before kill them I think you can still be quite "a bad guy" and laugh in a crazy insanely way.
To name some of the things i do remember of reading in the old forum, perhaps it can inspire you:
This traveller entered a city and as their not-hostile inhabitants welcomed him, he started killing them all for fun. Obviusly, this heavy armoured character was getting bored of this easy bloody task, and after killing a little child he used him as a throwing weapon. The message console displayed something like this: "You throw the grisly child corpse".
But the fun was just beginning, and for his surprise, this "new discovered weapon" made a house-wife get killed by a neck facture as the heavy weapon landed over her head.
So, perhaps it doesn't seem so maniac or psycho or devilish or whatsoever. But if you place yourself in that scenario you can get the picture, the feelings, what an spectator (her husband... the children's granpa).
Let's make shorter the next example, it's getting long:
This player (youtube video, older version) was the kind of "maximize your oportunities at any rate". He's chosen the scenario of Unfortunately hunting trip, where his dad was killed by some dangerous animal.
A 16 years old boy going hunting to learn with his father. The beast attack and finally kill the parent. But the child just butcher the corpse, laughing cause he got some nice slices of meat.
As long as you connect with the game, you can picture really complex scenarios. Where you can act in several ways. Cowardly, "heriocal", cold-hearted, benevolent, etc.
Lastly, i agree with the srukle 100%, That dichotomy perhaps could apply "Vietcom" or any war game. Where you can be the Freedom's soldier or the opposite (A.K.A. Vietnam, Nazi, CCCP, etc, etc). But of course, not only limitated to those.
UrW is not made to taste blood, to do GTA stuff, to be an hero or to be the bad guy.
Eventhough, perhaps you could be a really bad ass, bloody psycho in there.