Season 3 of Invincible will still have a significant role for Omni-Man (J.K. Simmons). The character had a pivotal role in the shocking conclusion of the first season of Invincible, as Mark came to learn that Omni-Man had been plotting against mankind covertly for his entire Earthly existence. Omni-Man attempted to atone for his sins on a different planet in Season 2, Part 1, but now he and Mark are at odds once more over his efforts to keep an alien planet safe from Viltrumites.
In the second half of Invincible season 2, Omni-Man is crucial, and he probably will be in the following seasons as well. In an interview with Sources, Simmons clarified that, despite his expectation that the focus of the program will frequently stray from Omni-Man, he still envisions the character being in the show until season 3.
Since Omni-Man is driven by his bond with Mark, a significant portion of Invincible Season 2 has been devoted to exploring his possibilities for atonement. The events of Omni-Man’s treachery dominated season 2, and Omni-Man’s activities in the war against the Viltrumites will continue to have a direct impact on the future Invincible season 3.
As Simmons noted, Omni-Man has always alternated between being the main emphasis of Invincible and being completely absent from the series he has traveled to other worlds and extraterrestrial planets, yet he always comes back to perform a crucial role. Every choice he makes has an immediate effect on Mark and Earth. Not including the character would be equivalent to not providing a connection that may potentially cause a great deal of difficulty in the future.