Master Yi: Alpha Strike is ridiculous
Master Yi's alpha strike ability makes him untargetable, and also immune to AoE damage, and his a ridiculously low cooldown. It is literally an "outplay button."
...he has an additional ability that makes him immune to CC as well. No slows, etc. So, the character is unstoppable and unkillable.
What I think about this can best be described by giving Alistair a box of bran muffins and a pot of strong coffee. This character goes back to the top of my automatic Ban list until he gets a rework.
Is untargetable for Yi most of the time