This question is a personal one. I feel like going in circles inside my mind, so I might as well formulate it here for my peace of mind. Apologies if it is not in the right format, or if it does create discussion rather than precise answers.
Academia is rife with bullying, and there is little doubt about that. I have been to counseling to deal with the effects of the lowest self esteem that I found myself in, during my previous job. I couldn't be promoted, I was actively avoided by the colleagues in my research group and my (many) requests for collaboration shunted. Counselling helped a lot, and it made me stronger and more resilient. I found a better job, including the promotion I was after, and now I am well respected and have a group that I can call 'home'.
I was recently called on a duty by a former colleague (nothing fancy, just reviewing some papers for them), and I was tempted to spill all the beans, an aggressive reply and Close the door to the past. I slept on it, and the morning after I accepted the duty. Now I finally realised that the grand scheme of things was for this same colleague to boot everybody else, and become head of the group there, with only lower ranking colleagues around.
So people, what to do... a bloody (well, relatively speaking) revenge that lasts a second but cleanses my soul, or a forgive&forget attitude, swearing not to become the same despicable bully myself?