300K just now. One of those "oops, wrong gun equipped!" moments.
Did not hurt as much as 60K though, at a time when that would have been enough for about 3 levels.
Worst "levels" type loss was my very first loss of the game. Lost over 9K fighting Father Gascoigne when I still couldn't figure out how the bloodstain/posession stuff worked in the first few hours of the game. Lost every soul I had earned to that point and had not leveled up yet. Would have been enough for at least 10 levels at that stage.