For me it's some champions that can miss their entire rotation/main damage ability, and still kill you without punishment.
Zoe, if she misses her Q even if she hit the bubble (which is so astronomically bad) can still hit you for extra damage. I find that dumb because all it does is remove punishment that SHOULD be there. This applies to say, Ahri too. She can miss an entire rotation and still kill you with her R and ignite along with her auto attacks, but that's a bit less stupid.