For me its Metroid, and really the whole Metroidvania genre. I can never tell when a challenge is supposed to be possible, or if I'm supposed to come back later, and and up wasting hours trying to do something only for it to be trivial later. I don't find this at all rewarding.

That said Tunic was a fantastic game, and I love the concept of the 'Metroid-Brainia', purely because of the concept that every challenge is theoretically possible from the start, you just need to learn how to do it.