@Z218: Yeah, I'm aware of that. But I was getting at the fact that she considered him as her father. For some people stepfather/foster-father/whatever-else-father still means father to them, so in this relation we can still say that both of their fathers were evil. Hence why I said that for me DmC Kat = DMC's Lady (just minus all of the fancy asskicking). Both technically kill their fathers also (well in Lady's case that's debatable) but she does shoot him at the end of DMC 3 when he still appears to be alive. And if Kat's foster-father was an actual demon, how did Kat manage to kill him? Because as many have pointed out, she never shows any display of her physical power/capabilities. Yet apparently has had some training in fighting and was able to kill her father who was actually a demon.
Your thinking more in video game terms of the big glorious fight to death type scenario where I'm thinking, its more anti-climatic as in she got lucky one day and was able to kill him when he had his pants down (metaphorically/literally).