What’s a monster your party has encountered, fought, then were lucky to escape alive from and never wanted to face it again?
Mine would be Bakunawa, which they encountered as a serpent goddess for a tribe of lizard people. She appeared as a beautiful woman to the Barbarian, who was quick to attack. She proceeded to mop the floor with the party through strong hits and stealthy skirmish tactics, but a few good rolls brought her down to near death, upon which she disappeared into the swamp. The party breathed a sigh of relief, some of them were near death, and chose not to pursue her further. Anytime it’s brought up since then the Barbarian’s player cringes a bit lol