Champion's Sword (5e Equipment)
From D&D Wiki
Weapon (Any sword with the finesse property), rare (requires attunement)
An elegant piece, grip, guard, and blade all gilded with precious gems and bright gold. A skilled user can initiate flourishes so blinding that they become untouchable. You have a +1 to attack and damage rolls with this weapon.
The first time you hit someone with this weapon on your turn, their next attack against you has a negative to hit equal to half the damage you dealt, until the start of your next turn.