I thought about it and based off how dragonball works, I don't think anyone could beat OMNI. What I mean by this is...Beerus is a casual universe buster. It's to the point that fist fighting with him and God's is destructive to their entire Universe. Even with this kind of power he is a weak feeb to King. Nothing. Not even a speck of dirt. Then we go on to other levels like Whis who can casually take out a universe killer with a single holding back hit. This means that Whis is FAR more powerful than Beerus, a casual Universe buster. Whis is still a flea to someone like OMNI King...not even a challenge. Then we scoot up to his father, Whis father who is multitudes more powerful than Whis who is a champion over a casual universe buster. Whis said that he doesn't register to his dad when it comes to power and that speaks VOLUMES because this same guy is a servant to OMNI King but yet he pales in comparison to power. OMNI King can kill all of these beings casually...instantly. Beerus also tells us that NO ONE could hurt him. This isn't the case in Marvel or DC. A Universe busters CAN hurt Abstracts. Hell, Heralds and trans tier characters can hurt abstracts in Marvel and DC but again, beings of this tier is snails to Universe busters (I wouldn't even limit Beerus to universe buster...he almost destroyed EVERYTHING). With that said, the power distance between a Universe killer in Marvel and DC works different. Someone like Beerus would be a high tier being in either Marvel or DC but he is nothing in DBS when compared to the kings of that Universe. I can't think of a single person in either universe that could stop him/OMNI King imo.