DnD Players: What was the biggest "How the fuck did you pull that off" maneuver in your campaign?

Spelljammer campaign at level 11. We were hired to get a MacGuffin necklace off of a pirate, by his rival. We waltz into his stronghold, get an audience, and then Nat 20 a Persuasion check to convince him for a 1on1 with my bard, b/c for a pirate so tough, what threat could my bard pose? His guards and my party members leave the room.

Land a Suggestion to have him hand me the necklace, and then land a Modify Memory to have him think it was his idea: we would claim he was dead, use the necklace to get an audience with his rival to show her "proof," and then double cross her and kill her. Then he'd swoop in, reclaim the necklace, and pay us handsomely.

Poor dummy. Hoodwinked!