I have an obsession with playing really difficult games just for the challenge. Since I am not a really good gamer, it takes me an obscene amount of time to beat some of these games. The most difficult game I have ever played is Sekiro (from the creators of Dark Souls):
I am proud to say that, after almost 6 months of playing for about 30 minutes every couple of days, I have finally beat this game. I probably only died a few hundred times (not exaggerating).