My female human barbarian was in level 17 when she got jumped by six fire giants in an unlit room. They shouldn't have been a problem normally, except she was burdened, so she used one turn to drop her bag of holding then used another turn to put on her ring of regeneration. These two moves cost her half her hit points. She finished off one giant and caused another one to flee, but caught up in the heat of the moment (I forgot to monitor her HP), she proceeded to fight the remaining giants instead of withdrawing. Death by carelessness, I'm afraid.
She was a promising character, having finished the Gnomish Mines and Sokoban levels, and was about to go on her mission. She had acquired all the usual intrinsics, was invisible, was stealthy (had Elven boots), had extra luck which did not time-out (luckstone from the Mines), wielded Firebrand (no enhancements yet because she only found one uncursed scroll of enchant weapon), amulet of reflection (from Sokoban levels), +2 gauntlets of dexterity, banded armour and cloak of protection. She had also identified most of the gems, armour, scrolls and potions. She even found three magic markers and an uncursed magic lamp.
Despite all her armour, her AC was a poor -6. Her pet dog, Fido, was polymorphed into a vampire lord in the Mines so it made short work of all the guards and shop keepers in Gnometown. Unfortunately, she let Fido kill the co-aligned priest of Crom, so she lost the opportunity to improve her natural AC by donating to the temple. That's a good reason to keep pets on a short leash!