Does the taste for revenge come from a desire that things had played out differently? Constantly dwelling on the event in question and wishing so hard that it had not gone the way they did. Playing things out in one's mind but changing them in a way that alters history so to speak.
I think this might lead to the vengeful one in question wanting to recreate the event just for the chance to have things go differently. Wanting to have things go differently to ease the pain that they were caused. Obviously such dark thoughts and wishes can lead to ruin.
Take for example any type of harm you can think of, let's just say A harms B in some way. If B were to follow this path they would want very badly for what happened to them at the hands of A to have happened in another way. B thinks on this and almost obsesses with it until they focus on easing their pain in terrible ways.
One could argue that maybe A deserves to be hurt in the way that B was but its not that easy. B stands a good chance of not only going after A but anyone that even so much as appears to be similar to A in the slightest way.
And that is only the beginning.