Fucking zubat.
Just minding your own business, walking through mt. moon, and bam! Zubat appeared.
It's level 5, my pokemon are level 20. I'll just flee, think I, not wishing to waste valuable pp.
But no, by the infernal hell-magic inherent in the zubat species, you can never, ever escape. And then it uses supersonic.
Sure, you'll eventually beat it, but by then your entire team will have taken so much confusion damage as to be near unconscious, and you know that in 5 steps you'll see another one.
If by some miracle you do make it through whatever dungeon you're in?
Gary. Fucking. Oak.