The one flaw Karsa has is he is so over confident, however he has really good reason to be so. I just loved this line in Reaper's Gale.
Karsa: "Should a god be foolish enough to seek to steal our spirits, I will kill it."
It really does prove my point about the over confidence, however he would stand a damn good chance at killing a god, so is he really over confident? hehe
I have loved the Karsa character since the first page he was on.