Vindictus has provided 2
first,
WAY back in early release, as in October i decided to tak on, at the time what was the boss that was giving me the most trouble, the lvl 8 Gnoll Chieftain boss, at level 16, mind you, at the time, i was really not that good with Fiona, and even at twice the bosses level and the best gear i could get, it still turned into a 16 minute battle, even recorded it

so soon as i get it on youtube I'll throw up a link so you all can laugh at how much i used to suck
second time
day 1 of the release of the Blood Lord raid, so, no one know how to fight this guy yet, and what do i do? talk my sis in to running him, with just me and her, and I'd not run it yet, yeah, it was brutal, took us 40 minutes of dieing (mostly me) to beat him, but you know what,

its also one of my favorite all time runs, been meaning to talk her into doing it again, same boss, just, with what ever gear we have now (at lvl 64)