It's wrong to seek revenge on others.
Fred was ripped off by a fast food place that double charged him.
Fred wants to avoid getting ripped off again.
Fred simply refuses to go to that specific fast food location.
Fred takes revenge on the location by standing outside and warning everyone they'll rip you off.
Fred can continue on with his life unencumbered by revenge.
Fred waste his time and effort on trying to take revenge on a fast food place.