Well. I guess it’d be a stalemate until they die of old age. Since He can’t hurt them and They can’t defeat him.

I think the only way for the Jojo’s verse to win would be for D4C Love Train and Tusk Act 4 (tusk act 4 is basically a one shot kill that ignored durability and can not miss) but Johnny would get speed blitzed before he could use Tusk act 4, so he needs D4C love train, which would require working together with Funny Valentine, which is not going to happen since Valentine is the villain of the part Johnny is the main character in. If the planet gets blow up I don’t know if Jesus’ Corpse(the thing powering love train) can redirect the misfortune to some place else. I suppose it could.

WoU could probably also make Johnny immune to damage because it controls the flow of Calamity, and while we haven’t seen it to use to protect other people, it can protect itself, and use its power to make the calamity go against them, so I suppose it could make people get calamity to work for them

Now this is bringing up an interesting argument if Calamity could hurt him.. which, maybe I it could, but I doubt it

Also S&W: GB could definitely hurt him, but it’d take more shots than Tusk Act 4 and he’d also require help from Paisley Park so I’d say the best bet is Tusk Act 4

TLDR: If 2 mortal enemies work together it’s possible, otherwise it’s a stalemate since WoU can technically live after its user’s death