[Gameplay] Yi's Highlander making him immune to all of Galio's CC?
When I was playing in Twisted Treeline as Galio against a team containing a Yi, he seemed to be able to completely negate my W - Shield of Durand's taunt by using his ultimate, displaying the message "Cannot be slowed!", and the same issue happened when I went in on him with my R - Hero's Entrance, displaying the same message and leading to Yi still being able to do actions, like Alpha Strike, despite the fact he was supposed to be knocked up at the time.
) You may have been seeing it float "Cannot be slowed" when he was resisting your AS slows rather than a movement slow.