Michael never tries to kill Loomis
Anyone ever notice that? Whenever Michael confronts Loomis he never gives him a killing blow, in this he just slashed his chest and tossed him on the floor and left him, and in Halloween ll he just sticks him with the scalpel once and leaves him. In H4 he grabs Loomis and tosses him through a window.
He'll injure him to get him out of his way but he never tries to really kill him. Its interesting, almost as if Michael can't bring himself to do it cause he's he's been his doctor all his life, maybe some tiny part of him cares about him.