Hmm I reckon if he fell far enough he could get hurt. He's never really fallen more than the height of a tall building, and in the case of Temen-ni-gru his descent was slowed by leaping on blood goyles, and ended with him being swallowed (so he didnt make impact with the ground). I'm not sure about death, but I reckon if he'd have hit the ground at that speed it would have damn well hurt.