"Killing an opponent" - Vampire's Kiss set
"When killing an enemy" - Vengeance leech set
"when a nearby enemy dies" - Necromance set
So a few questions. "Killing an enemy", what is that? Is dealing dmg enough, do you have to deal all the dmg, do you have to get the killing blow? And what is the range of the sets?
So far my limited testing with the vengeance leech set tells me I have to kill the opponent with a weapon skill to trigger the set.