The basics are hatred of women and having their characters raped, a misunderstanding of Trek leading to some awful storylines and characters (and Enterprise, as it was almost entirely his baby), he had zero TV experience save for a kids show, he was impossible to work with, he shot down stories for little to no reason, he was a bigoted piece of shit, he micro managed everything to fuck, he HATED gay representation and repeatedly shut it down, the show runner of DS9 had to actively lie to him to get the show made, he was an awful writer but insisted on writing anyway, he was toxic management type to the point of forcing names off of scripts and putting his own name on, pushed people to their breaking points, interfered repeatedly with everything in front of him to the point you can SEE the interference in certain episodes and was a particular cunt with contract negotiations.
That's not remotely all of it.
The correct answer to the post is that he is the villain.
If Gene is the great bird of the galaxy then Rick Berman is the Great Botfly.