Does it apply to the ending even if I kill enemies like guards from the point of view of Sean?

[ung45]

Except for the epilogue, I didn't kill the guards and saved my father, so I watched the good ending,
I think there's going to be a chaos system like Dishonored.

[Taberone]

I think the only kills that aren't allowed are Cops, Innocent Targets, and Civilians? I got the Best Ending even though I consistently killed all the guards on every mission, with the exception of the one time that the cops show up (instead I knocked them all out to avoid losing Trust with Steve). I spared all the Innocent Targets too. The game just doesn't care about guards, so feel free to kill them.

[Private Homestead]

If you lose trust for the action, they're off-limits.
For the most part, not killing people with Sean is for achievements.