Champions that require to hit a single ability to finish you off are extremely frustrating to face
: Hit R, doesn't matter how far you are, if you don't have 800 MR or a Zhonya, you're dead
has 3 "skillshots", but hitting one enables you to hit the 3 others (and been said numerous time, if her ult has the cooldown of a normal ability, it should deal the same damage as a normal ability)
E, just hit E
same, just hit E
hit E too
I don't have anyone else in mind so far (and I mean, guaranteed death after hitting such skill, not
R for instance), but yeah this has to be the most frustrating part for me

W. It doesn't kill you, but quite annoying to play against.