Lets not forget that him and Vegeta have god forms.

who never said gems like the diamonds or even two way fusions can also blow up galaxies? also i doubt goku can, stronger opponents like bills (or beerus, whatever you wanna call him) can.

The closest ANY Steven Universe character has displayed to DBZ levels is Lapis' water tower, something that put's her on muti-contenent level, which is far bellow the multi-galaxy of DBZ characters, and even further below Sailor Moon's Universe+ level

let me restate, who said that just gems can't destroy fusions?

also, the cluster

Gems can beat fusions (destroy would involve shattering the gems they are made out of simultaneously presuming that is what you meant), take Pearl vs Sugilite for example.

The Cluster is planetary at most. A DBZ character could probably one-shot easily. Once you get to Black and his presumed power no SU character really has a chance. The power difference between shows is gigantic.

that's assuming they'd even have a crossover and meet.

which is slim to none.

I think a better confrontation would be the dragon ball characters during the King Piccolo arc and the gems now.

I know its very unlikely, its just a hypothetical topic.

Forget it, what would they say to each other if they met? I think Black would give them the same reason he give to Trunks why Humanity need to be destroyed and call the CG's fools for protecting Humanity.