I think a few people got it right when they said that, the various Karma systems are not your character's "Good/Evil" tendencies, but more or less on how the public perceives your actions, and how it affects them 'directly'.
Like when someone said that the public sees Moriarty as the lifeblood of Megaton, regardless that he's basically just a vindictive and manipulative piece of trash, he still supplies the settlement with it's raw needs. So, sure, on the level.. it's good he's dead and it frankly doesn't deserve any negative karma, but Megaton suffers to an arguably greater degree, as someone now has to pick up Moriarty's rather challenging responsibility. It's not like his competition, the drug-addicts with burning holes in their pockets are going to pick up the slack, catch my drift?
So the public, for better or for worse, suffers, on the terms of the wasteland.
Tenpenny, abuses the entire wasteland, and the only public that would suffer to his loss is the residents of the tower. Who happen to be just like him. It can be argued, that it could fall in the same lines of Moriarty's karma hit, but virtually everyone outside of Tenpenny Tower in the burnt-out District of Columbia hates that fucking place and everyone in it. They're the equivalent of a Machiavellian secret-society in our present time, who weave schemes of destruction for their personal gain.
With Red Dead Redemption, it's also not good or evil. It's just "Honor", and that's a damn loose term in the wild west. It's basically all about shooting who deserves it, and who doesn't. If they draw on you, and you waste 'em, it's considered honorable. It's a big, big.. Big sandbox game world.. so you're going to run into situations where honor is subtracted or added wrongly, it's not like the system can be perfect. You wanna talk about hard work... it would be virtually impossible to make every single thing you do factor the way it should. Go ahead and try it, if you think it can be done.
RDR just uses Fame and Honor. Fame is for anything, it's androgynous basically.. so you can be a famous lawman or a bandit, or both. Doesn't matter, people just know who you are. Also, it's not like + or - 100 honor is anything drastic in that game. It can be moved in any direction fairly easily.