I got one for each expansion basically:
Vanilla:
AQ40 was horrible due to the longest corpse run ever from CTHUN and all that stupid thrash
TBC: everything was fine, maybe magtheridon and his no.. not again! and all the "sorry misclick! -->wipe"
WOTLK: TOC was horrible and ruby sanctum thrash was stupid ...
CATA: noone remembers Thone of 4 winds? jump, puddle, jump again more puddles .. And Alakir was so overtuned for 25 men hc it was kind of "i will do this once for achivement and never come back" including the most ridiculous loot system ever.