Omni-Man's planet-level power and FTL speed make him virtually impossible for Batman to defeat.
Batman has defeated Superman-level threats through kryptonite and preparation, but Omni-Man has no known exploitable weakness comparable to kryptonite. Viltrumites have vulnerabilities to certain sound frequencies and the Scourge Virus, but Batman would have no way to know about or acquire these without access to Invincible universe resources.
Omni-Man operates at FTL combat speeds and can crack planets. Even Batman's most powerful suits โ the Hellbat armor, Justice Buster โ are designed to fight specific DC threats with known weaknesses. Against an unknown Superman-level threat with no clear vulnerability, Batman's preparation advantage is severely limited.
The raw power gap is enormous. Omni-Man could destroy the entire Batcave, Wayne Manor, and Gotham City in seconds. Batman's gadgets, martial arts, and tactical genius are irrelevant when the opponent can fly through mountains and shrug off nuclear weapons.
Batman has contingency plans for every Justice League member and has defeated Superman-level threats before. His tactical genius and resources could potentially identify and exploit Viltrumite weaknesses given enough time.
Omni-Man has no easily exploitable weakness like kryptonite, operates at FTL speeds that negate Batman's tactics, and can crack planets with his attacks. The power gap is astronomical and there is no clear path for Batman.
Omni-Man wins overwhelmingly. Without a known vulnerability to exploit, Batman's preparation advantage is nullified. The physical gap between peak-human and planet-cracking Viltrumite is simply too vast.
Batman also fights
Omni-Man also fights