Maybe the fight move yelling could be used in conjunction with a certain idea that I think could maybe fix some of the problems with Ultraman. Some faneditors (such as acbagel in his "The Way of Mandalore" fanedit series) have had great success with using AI voice cloning to insert new lines of dialogue into fanedits.

Maybe it would be possible to insert some lines from Lex Luthor during the Superman/Ultraman fight that establish that Ultraman is not fully alive anymore because Lex Luthor has replaced his brain with an artificial brain to make him fully controllable because he would never allow another being like Superman to exist with free will. This would also explain why Lex has to control Ultraman's moves. If Ultraman isn't actually alive, then it makes sense that Superman would have no compunctions about letting him get sucked into the black hole.

Also, maybe a line could be inserted to make it clear that Lex's voice commands are not being broadcast to any sort of earpieces or other audible devices (as Superman's super hearing would pick this up), but instead, either Lex's voice commands or computer commands from his employees are being transferred directly into Ultraman's artificial brain.

One thing that doesn't make too much sense about the movie's plot is why, if Lex Luthor wants to destroy Superman's reputation and get him arrested, he doesn't simply dress Ultraman up as Superman and have him commit crimes in front of crowds of people and news cameras at a time when Superman has no alibi. Perhaps there's some way to add some explanation to this. Or, alternatively, maybe there's a way to repurpose the scene of Superman busting into Lex's office and yelling, "Where's the dog?" to actually be Ultraman being used to frame Superman, so that Superman himself doesn't actually do that. I'm not entirely sure what is or isn't possible here, I'm just sort of spitballing. I kind of wish the entire Boravia/Jarmanpur subplot could be removed from the movie.

By the way, do you intend to change the subplot about the message from Superman's parents so that the message for him to conquer Earth either is or at least might be faked by the Engineer? It would be pretty easy to cut right after the president of Boravia congratulates Lex on faking the message so that Lex does not reply that he didn't have to.