Season 12: Lou
In season 12, Meredith gets attacked by Lou (Dohn Norwood), a patient who was in a fugue state. Though the attack renders her unable to talk or walk for a while, she forgives him since he wasn't aware of what he was doing. It's a pretty touching moment as we consider it in juxtaposition with all the love and support surrounding her even post-Derek. About a quarter of the episode is in silence, as Meredith loses her hearing temporarily. It's one of Grey's Anatomy most powerful episodes, that's for sure.