A lot of games, most of which I don't really recall.
My most recent 100% was Catherine, which is one of the most balls-hard 100%'s I've ever done and I enjoyed it from start to finish. Gold'ing all the stages on Hard, the huge pain in the ass that is Rapunzel's 128 Stages followed by the extreme difficulty of the Babel Stages was something that took me well over 50-60 hours to do.
I even did all the Babel stages in both Solo and Pairs (playing with both controllers on my own of course, you think I have friends?), which is completely unnecessary for 100% but just something I felt obligated to do.
These days, I've been trying to improve my high-score for the Babel levels. And at this point I actually have the #1 European Xbox 360 score for Solo Axis-Mundi. If that ain't 100% completion, I don't know what is.
Persona 4 wasn't a hard 100%, but a long one because getting the Persona Compendium filled out just takes a long time with the wiki more than any relevant skill. Most of the personas are useless anyway, you quickly fall into the combination you like. It was a 100% I couldn't be arsed to repeat with Persona 3 Portable which I played later on.