Something chaotic happened --- sorrow if this double-posts.

You're right --- I can't think of a single instance in which Ethan killed, directly or indirectly, anyone on his own. However, there is an undeniable sense that he has killed in the past by the time we meet him. I never felt like he needed to kill as in the sense of a compulsion, but he would if it heightened his sense of pleasure in chaos and anarchy.