How do I politely tell HR my colleague is an incompetent bag of dicks?

Hi yall. So I’m in the middle of writing my resignation letter. I work or I guess used to work for a VOIP company, not gonna name them they don’t deserve the free advertisement and am quitting due to a colleague that has the mental capacity of a potato but the confidence of Johnny Bravo. Anyone here have experience with this? Is including this in my resignation letter wise or will it backfire? Thanks in advance!