Undo

As a reaction, you are able to cause the last turn to be undone.

The spell can affect a single creature you see within 60 feet, including yourself.  The affect of the spell is to reverse the last turn (move, action, bonus action), so the target of this spell must have just ended their turn when casting this spell.

Once the target's action is undone, that creature loses their turn, they are moved back to their original position, and any damage or other effect caused by the creature is reversed.  Also, any resources used (spell slots, potions, etc.) are returned to their original state they were in before the creature's turn.