Got an archmage going - gnomish wizard, then got super lucky with Mana Battery as my first corruption so I thought I'd give an archmage run a go. All went well, after much tedium I had a level 46 wizard with 99 in all stats, all skills at 100 except fletchery (which stuck at 66), weapon skills all to ~10 or 11 except swords which was at 13 (again, tedium), all instrinsics (except invisible because that just wasn't happening for some reason and I got bored), half a dozen amulets of life saving and a bunch of other equipment, just shy of 30,000 castings available of acid ball at a very high skill level, and between thousands and 30k castings of most other spells, 1.2k HP (really should have gone for more), nearly 8k PP (largely redundant by D50 due the mana drain), and speed of about 1040 even in moloch armour. That speed proved a mistake to go for so early - leveling up became a nightmare. I ended up going to the first level of the Putrid Caves with a couple dozen danger scrolls and casting slow on myself for a few evenings until I eventually levelled up (wishing for emperor moloch quickly stopped netting any significant xp; slow had a huge effect on increasing xp gained in the cave).

Got all the stuff for an ultra ending (a very very quick kill of the emperor moloch and filk), headed on down, read through the wiki a few times and was all set. Cleared the room with the chaos portal with maybe 4 or 5 acid balls. Checked my inventory, got all items equipped, then decided to just get on with it and dove through the portal. Forgot to increase my alignment back to L+. Died.

This sits tied with the time I ate the corpse of Pestilence the first time I ascended to the Astral Plane in Nethack.