Anyone capable of destroying something that size, but while it fights back. Destroying a city, for example, is far easier than destroying a city-sized foe trying to attack you.
How large is the worldship? If, like the name implies, it's the size of a planet, you'd probably have to go to planet-buster level (generally High Herald, give or take) or higher to find a good matchup.
Well damn, that changes things. I suppose we're assuming for the sake of the thread that Jack can interface with it just like a normal city. Because technically speaking, large cities (Mexico City, New York, Tokyo, etc.) are about the biggest thing he's ever used.
But presuming that that's the case, then you'd need actual star-system destroyers, because the ship (thanks to Jack) could be self-healing, and utilize whatever weapons it already possesses, as well as being beyond gigantic and angry as hell. Sub-Skyfathers would probably be a minimum for making it a fight. The Surfer's and Thor's of the world could put up a fight, but I'd give a majority to Jack over nearly anyone this side of Odin.
He became above sky-father by downloading information from the Worldship. It seems that the ship itself can control the cosmic power to a high level, so it can give limited omniscience and great power like it did to Korvac.
(There are other times this has happened, as when the cosmic Red Skull wanted to become omnipotent)
yup, simply interfacing with galan's worldship the Taa II made korvac the "machine god". korvac was just a normal guy, but a man like manhattan can become one with his environment, not saying that means he will also ascend to godhood but that strictly depends on the makeup of the worldship.
I think Surfer might actually be able to pull off a 10/10 win against Jack in this scenario.
He'd have to fight him on the astral plane though, thus negating any advantage jack gets from melding with the Worldship.
Furthermore, are we to assume that Jack will simply obtain cosmic awareness without any problems?
remember, it's driven better/greater "men" insane, just simply attempting to cope with the kind of CA that Galactus (and presumably his Worldship) has.
To be fair, Korvac was not exactly a normal guy, his machine parts were very good with calculations -such as analysing Grandmaster's powers after seen him once-, so it is entirely possible that Jack is unable to cop with the information. It really depends if his ability to communicate with cities can increase the number of things he can think about -boost his intelligence at the very least-.
He's never had a problem with massive amounts of sensory input, which he receives when he's in a city. Most of him technically isn't human, since he's designed to be able to interface with such bodies without problems. To be fair, he's never interfaced with something this large, but the only thing that gives him head trauma is when a city undergoes massive amounts of damage....as in, a large majority of it is destroyed. Destruction of large buildings, streets, sections of cities, etc. do nothing to him.
Saying Surfer wins 10/10 is obvious bias. Against his master's ship, one that apparently made Korvac Skyfather+, I'd say even a majority for the Silvery one would be a stretch. High Heralds could compete, certainly. But likely wouldn't win much.
All of this, again, presumes that Jack interfaces it with the ship efficiently. Otherwise we have a non-thread.