Nightcrawler can teleport and take other people with him.
In the Age of Apocalypse Saga we saw a cruel and dark version who would simply teleport parts of his opponent's bodies away with him.
So yeah he can teleport people's heads off.
Even when they were trying to save Hope from Bastion and the Nimrod's, he teleported one's arm off. Also at a distance of I think 500+ miles? Which is further than he's ever ported before.
Nightcrawler's powers, being psionic in nature, probably allow him to mentally control his powers so that he can teleport literally what he does and doesn't want to.