I think it's been enough time for this to not be a spoiler about Avengers: Infinity War. But still,
So, at the end(ish)
Thor takes his mighty axe and slams it into Thanos, deliberately not killing him so he can gloat about it first. At which point Thanos says he should have gone for his head and clicks his fingers anyway [possibly ending life] for half the universe.
I understand, to a point, why didn't Thor go for his head (in Thor's logic anyway), but why didn't he just bring the axe down on Thanos' left arm at the shoulder (which he was close to anyway) removing his arm completely, both keeping him alive for Thor's chance to rub it in his face, at the same time preventing him from operating the gauntlet as it would be on the ground and thus, inoperable by Thanos?
It's a semi-plot hole that's been bugging me since I saw the movie for the first time way back when, but I've not seen anyone else bring it up, nor offer any theories (other than narrative for all the movies) why that wouldn't occur to Thor.