I've actually played something harder.
Can't remember what it was though. It was some weird game where you played as a dragon and had to get lemonade.
The first 2 levels were easy as hell, but level 3 was all "HOLY CRAP INVISIBLE SPIKES EXPLOSIONS LIGHTNING FAST ENEMIES A CRAZY DUDE CHASING YOU!"
But yeah, other than THAT game, I Wanna Be The Guy is the most unfairly hard game in existence.