If Mongul appears in a Superman sequel, I hope they adapt or use the storyline
"For The Man Who Has Everything".
https://en.wikipedia.org/wiki/For_the_Man_Who_Has_Everything
Yeah, that is one of the all time great one-off Superman stories. I think they did an adaptation in TAS.
My only problem with Mongul is that he's kind of like a second rate Darkseid, not powerful or evil-genius enough to be the lord of Apokolips, but pretty good as a supporting villain in a Superman story.
As such, I don't know if there's room for him in the DCCU.
In an animated film I think Mongul would be great, but in live action, his look would be tough to pull off -as convincingly menacing and powerful, without looking too Dark-seid ish. Plus, he might end up looking like a yellow Thanos - which would not be a good way to go.
Also, there are other really iconic Superman villains who should probably go onscreen first - Brainiac, Bizarro, Doomsday, Metallo, Parasite - before Mongul.
He's on the list of top Superman villains, but I would rank those others ahead
of him. I guess if he was going to appear in a film, it would be as a supporting villain, IMO.
Personally, the most challenging villain to bring to life live-action, would be Mxyzptlk, without getting too comedic.
So, all in all, I think that Mongul should be left out of the live action DCC, although I would love to see him either in an animated film, and I think the next time there's a live-action superman tv show ( come on, there have been heaps of them, so there's going to be another sooner or later) and Mongul's the kind of character who could occupy a multi-episode story arc.
- I remember the classic 80's superman story, where he left earth and ended up as a gladiator on warworld -cool stuff.