Well I would say..
1. With a good character and two angels to aid (cloak of electricity resistance +5 i think) in the zombie level a master necromancer which I couldn't see beheded me with a burst of lightning. It was horrible because although I had Amulet of Life Saving I didin't had my second life as he destroyed my head. :S I guess the electricity resistance didn't cover my head also...
2. Polymorphed into a cave bear in UT2 (500hp) and when entered UT3 Izzy appeared and owned me completly.