The damage is different too but I’m just curious
Revenge
Revenge deals damage and is a decreased priority move, causing the user to attack after other Pokémon that are using ordinary priority moves. If the target had already damaged the user in the same turn, Revenge's power is doubled to 120.
Payback
Payback inflicts damage. Its power doubles to 100 if the user moves after the target, if the target switches out, or if the opponent uses an item.
Retaliate
Retaliate inflicts damage. Its base power doubles from 70 to 140 if a Pokémon from the user's party has fainted in the previous turn.
They are quite different.