I recall one time Loudmouth McGuire was betwern the benches during a game against Colorado, and supposedly word went down the Avs bench that 'Kovalev doesn't want to go tonight' - which had a big confidence-boosting effect for their players. Everyone knew he could kill you single-handedly, so a lot hinged on his whimsical moods.
My own favourite Kovalev moment was when he took Tucker's head off late in a game against the Leafs. The only comparably cathartic moment in recent years was when Subban destroyed that p*ick Marchand with that shattering open-ice hit.