I haven't seen all the Flash Gordon comics. I have seen the serials, but I know the serials were based very closely on the comics, so the comic books would be the primary source for any Flash Gordon stories.
I know Flash faced different "minor" enemies, mostly on Mongo. Often they were princes or princesses who didn't want him trespassing on their land, but often he ended up making friends and turning these minor enemies into allies.
Throughout the comics that I've read, the major villain, always overshadowing everything Flash, Dale, and Dr. Zarkov do, is Ming the Merciless. Is he the only major enemy Flash ever faced?
By major and minor, I'm thinking about how Flash, even when Flash was in trouble with a minor villain, he still had to deal with the real big bad guy, Ming — so were there ever any other major bad guys other than Ming?