You don’t have to fight a bully to beat them. You just have to make sure they’re not the loudest voice in the room.

The power in a situation like this runs on attention and volume rather than strength. Fighting hands them the contest they are already set up for, and it usually costs you more than it costs them. What actually undoes it is the room containing other voices: somebody talking normally, somebody not laughing, somebody saying the plain thing.

If you can, say one ordinary sentence to the person being targeted while others are around. Then bring in an adult who has some authority over it. You are not supposed to be the only line of defence here.