Removing Master Yi's immunity to attack speed reduction on Highlander
Title.
Seriously, if he finds you, you die (twice as fast if he's Sated). With that being said, given how much his damage spikes, I don't think it's unreasonable to allow Randuin's and Frozen Heart to actually be useful against something that strong. I don't believe any other champion is capable of immunity to attack speed reductions, though I could be wrong. Immunity to move speed slows is fine, immunity to attack speed reduction is not. Not in 2015. Not Sated Master Yi. No.
EDIT: or anything else that slows attack speed (e.g. Nasus Wither)