So you got a better job and are about to give notice? Great! Just please keep it straightforward and tell your boss you are leaving and talk about dates for your notice period. Do not give gifts or write notes. Don’t download on this co-worker.
If someone from HR wants to do an exit interview with you, you could say some general things about the work environment (which sounds like a middle school to me, tbh), but again, do not dump on specific people.