Quick question: Do we get to kill anyone? All's fair in love and war.
To some extent, you may have already done so, albeit indirectly. If you're talking about a direct way, I think anything's possible over time.
Though considering most games are built around violence in one way or another, you could mean something like that - going around, killing stuff, and getting exp. Then, hmm... Let's put it this way: I wouldn't expect Selene to pick up a bronze sword and go killing faceless masked villains one day. Sure, it's convenient when an enemy is just a baddie, a walking piñata of your legitimate exp. You just have to hit him hard enough, and he'll shower it all over you... Along with his bloody guts. But it's quite different when this
"baddie" has a spouse, children, and even a loving mommy, and not just Strength 18, 250 HP, and Mace of Mysterious Bullshit +2. And it's even worse if he has his own truth, not a meaningless desire to destroy the world in the name of another Evil Overlord or something. However, even so, I still don't see any way to keep you from killing him in that hypothetical situation if that is what you really want to do.
And, as an example and partial answer, don't forget that I allowed Selene to finish off one crawler in a very sadistic way, with detailed descriptions, not cowardly euphemisms. That wasn't really necessary. Yes, Selene, in that situation, can choose more humane ways without causing a living creature so much pain for no good reason. Or even throw it back into the water. Still, it's in the game as it is. Because it's up to the player to be Selene a good girl or a sick bitch. My job is to give opportunities and work out the most likely consequences. And not judging from a high moral ground of what people do in imaginary situations, limiting them there of what I think they should do.