I don't think there are any negative effects for killing enemy soldiers. There are, however, negative consequences for killing innocent Talan civilians.

The different opinions of Zokrym and his son become relevant to the plot, but are not related to player choies that I know of.

However, if someone else has any information to the contrary I'd be interested to hear it!

The player is allowed to kill soldiers, the oppressed Talan usually support that. But the game does leave you the choice: do you attack and kill all the time, or use stealth as well? Basically, it's up to you to play your role.

Using violence against other NPCs though is a big no-no.

Using violence against enemies is fine. If you shoot too many friendly NPCs, they will eventually like you less and stop helping you, but you'll have to be a psychotic mass murderer or a really terrible shot for that to happen accedentally. You can still complete the game, but you'll receive less or no hints, depending on how many friendly Talan you've killed .

There are a lot of different answers you can get from NPCs depending on how much you've helped them and how many innocents you have killed. I think there are about four different levels of support: 1)They worship you (you have completed a bunch of quests and barely hurt any friendly NPCs)-> you get full support (this is what you get when you play the game normally). 2)They like you but not all are convinced you're the saviour (you haven't hurt any innnocents, but haven't completed a lot of quests yet -> you get more or less full support (not completely sure, but it barely makes a difference in my experience). 3)They're sceptical (you've helped them, but also hurt too many friendly NPCs, I think it's enough to kill a few friendly NPCs to get to this level, you can propybly get on better terms with them if you solve more quests and stop hurting them). 4) They dispise you -> only the minimum support from key NPCs necessary to solve the main quest, maybe not even that. Others refuse to help you and don't give you directions and info anymore. (You pretty much have to go on a killing spree for that to happen though).

tl;dr Shoot enemies as much as you want, try not to hit too many friendly NPCs and you'll soon be worshipped as the Ulukai