For me it's got to be the time the BBEG's cambion lieutenant came into town to give a dramatic and intimidating warning speech promising doom if the PCs continued to oppose her. The effect was somewhat lessened by the party arcane trickster using Mage Hand to pull her hair, poke her eyes, pick her nose and stick its fingers in her mouth. She couldn't even retaliate because she'd come alone and there was no way she could stand up to the party by herself. She ended up Dimension Dooring away in shame.

Later when the party actually fought her she died while prone and paralyzed from the party paladin crushing her armour and chest with his warhammer.