I think ppl make size differences out to be a larger issue than they are. Unless a character is LITERALLY GARGANTUAN compared to the other, the size can generally be evened out/coped closer. Kirby characters are a perfect example of these, they’re all 8 inches tall, Sonic characters as well, they’re only about 3 feet. And ONCE AGAIN Ultraman can change sizes from regular human to giant, so he could be normal sized for like half the fight.
There’s also plenty of ways to make a giant vs a regular sized person interesting in combat, you just have to be smart with your choreo and work with that in mind. Gohan is an incredibly mobile character with long ranges attacks and matches Ultraman’s power, boom, that gives him what he needs to work around it. Hell, you could have the fight be him actually having trouble managing his giant form until pulling out Beast and finally being able to rival him despite the side difference.