Kangaxx the lich owned my ass for the 1000th time.
1) Protection from Magic (Ribald, for around 1k) or Protection from Undead and Carsomyr.
2) Berserk + whatever +5 weapon you can get at the time.
My main character's a berserker, and I have a paladin who just got Carsomyr. I dropped four traps where kangaxx spawns, to get rid of his "lich" phase, then when he went demi, I berserked on my main char and used a protection from undead on my paladin (the only person with a +5 melee weapon... actually probably the best weapon, as it dispels on hit) and whacked away. Kangaxx kept trying to imprison my main char (as he was closest), but the berserk prevented it from happening. My paladin whacked away with about three 2-3 damage hits every round (oil of speed), and eventually he kicked the bucket. No casualties! yay!
I usually don't like tactics that use above a certain amount of cheese, but I made an exception for Kangaxx, as he throws out imprisonments like free candy, and those... well, they're like King cheese.