Taunt is definitely the worst since you get things like Galio and Rammus where you are then severely injured for attacking them, even if they do nothing else.
However it is also balanced since it is generally on a short range.
Fear and taunts just cause more rage since your champion is actually acting against you, instead of standing there with a stun. "God ****it, don't run there! I - OH GOD IT'S YI!"
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