Don’t you just hate it when you see someone thriving after they have done you wrong? This could be an ex or an old employer or whoever. Do you just get that little twang of jealousy in your body even though you are in a fabulous place, to just think, what a piece of crap they are?! Have you ever thought of doing something to attempt to jeopardize that person for your own selfish reasons? Do you think it would make you feel better?
Retaliation is the return of like for like in actions, revenge is harmful action towards a person or a group because of some sort of grievance. They sound different, but they are very much on the same playing field and should be avoided. Karma does exist and will come back one way or another to harm you. And it is not worth it to put yourself in that position to possibly hurt someone for no reason other than you are pissed that they are thriving on your ideas or doing what you have always done and doing it better! I know it stinks, but this is life and not worth it. Live your life and love what you are doing, you will get what is yours in the long run.