Over at the OS/R Discord, we have been playing Lamentations of the Flame Princess through a few iterations. And if you look through any of the games at the protagonist characters, you'd be hard pressed to find anyone with any redeeming characteristics. Most have been brave in the face of monstrosity, but there are not characters you'd invite over for gaming night. At least not if you expected their behavior to be within social norms.
On the surface and to some degree by design, Lamentations characters exhibit a high degree of anti-social behavior. They are looters and treasure hunters and monster hunters after all. None of them, that I have seen, rise to the level of say, Geralt of Rivia, in terms of pretending not to care, but in fact caring when the chips are down. I would say they have been terrible people with a basic lack of empathy, almost to a man.
But, and I think this is important, most of them have been 100% sane. Maybe 98% sane.
Neither Lamentations nor Fifth Cycle have any kind of humanity mechanic. There is no trip wire that tells the player that their character has crossed the line; there is in fact no line save any installed by the group. A social contract can (and should) tell the player where everyone's limits are, but how often do people discuss an issue like this?
In a couple cases players have expressed both fun in playing their characters, but a revulsion for playing such villainous individuals. I have seen this myself; playing such an extremist requires a great deal of energy and would discourage me from playing the character for a long time. But the few sessions I do spend with such a monster are satisfying.
But if we are talking about a character with a mental disorder or some level of insanity, say a Malkavian in Vampire the Masquerade, that presents a different challenge. A game that erodes sanity might make a good charcter into a gibbering psycopth, but there is room to care about that character. A character that lacks empathy can make it harder for a player to invest emotionally in that character's success of failure.
I am curious how others see the dichotomy, if they indeed draw a line between them. We are planning on a longer reflection on the Lamentations play; I just thought this topic seemed relevant to some recent conversations and wanted to bring it up.