If you mean an omnipotent, omniscient creator, then no, Saitama cannot defeat him. Why, because Saitama is not strong enough? No, it's not that simple. A true omnipotent, by definition, has all strength and no weakness.
Saitama Beats God and Destroys the Universe
With that in mind, he determines the fourth dimension operates in the same manner. Saitama wrecks God's home and exceeds the speed of light, breaking through time and space, escaping back into his own reality.
With his ability to capture enemies into Imprisonment balls and his card attacks, he proved the might of his power and emerged victorious against many other gods during the exhibition match. Saitama could prove to be a formidable opponent, but sadly, it is likely he will not be able to conquer the God of Universe 11.
When Saitama, Flashy Flash, and Manako peered through a hole while they were underground, "God" seemingly appeared to be in another dimension and it looked like an extremely massive humanoid entity, so much so that it completely dwarfed the hole they peered into. However, none of the three could see it.
That is, God's height is approximately 84% of the Moon's diameter. If the Moon in the One Punch Man universe has the same dimension as the Moon in our universe, that is, considering it a perfect sphere 3,474.8 km in diameter, we have that the height of God is approximately 2,921.4 km.
The only event that came close to becoming a God-level Disaster Threat was the meteor in the first season, which Saitama managed to stop easily. Otherwise, for now, it seems like the only God-level threat that the universe might face is from God himself, who has made himself known numerous times in the manga.
Lord Boros
Although defeated in the early stages of Season 1, Boros earned his way to the top of the list for being the first opponent to truly put Saitama's skills to the test.
Based on whatever information we have so far, Saitama is undoubtedly one of the strongest, if not the strongest character in the series. He has the ability to take out some of the strongest villains with a single punch. Boros was one of the strongest villains introduced in the series.
The Tournament of Power shows that Zeno can erase an entire universe, so whichever approach he takes against Saitama is still going to end in his end.
The character referred to as “God” in One-Punch man is an otherworldly being that appears to grant people power but at great cost. The well-drawn character has made its appearance in different chapters in the manga, puzzling fans on the true nature & goal of this being.
In One Punch Man Chapter 167, Saitama goes all out because Garou (Not Permanent ) Killed Genos. God probably didn't give saitama his power, he earned his power by removing his limiter. God does have the power to turn normal humans into dragon level beings.
Although he tells everyone he got his incredible power through mere physical training, no one believes him at all. According to Saitama, after a year and half of 100 daily push-ups, sit-ups, and squats, plus 10km daily running, he had achieved some level of superhuman strength.
Saitama has yet to lose any battle on screen, but in the manga so far there's been three opponents that Saitama has used more than a Normal Punch against. Beast King is very easy to write off, because he wasn't actually that strong.
A leading fan theory regarding the source of Saitama and most characters' strengths is that they trained and dedicated themselves to an inhuman level. The result of their high-level dedication is supernormal strength that is unusual for a human. In fact, many heroes in One-Punch Man can be linked to this theory.
4 King Is Saitama's Only Worthy Opponent
The two often hang out together and play video games. King is inordinately good at video games and beats Saitama soundly at every game they play. This makes King the only worthy opponent Saitama has ever encountered.
Blast is the overarching protagonist of One Punch Man. He is the S-Class Rank 1 hero of the Hero Association. Other than Saitama he is the strongest known hero of the Hero Association.
He is the S-Class Rank 7 professional hero for the Hero Association. In public, King is known as the "The Strongest Man on Earth" (地上最強の男, Chijō saikyō no otoko).
Being classed as a Dragon Level Threat or higher, Boros is a very powerful Mysterious Being, whose energy is powerful enough to blast away entire planets.
In terms of religious and biblical senses, no he is a mortal human. But, if you are referring to the ranking system in the O.P.M universe, then yes, he is considered god level.
Goku is an extraterrestrial being who has to lose a fight in order to get stronger. Saitama is a man that can defeat any foe with a single punch. If the two of them were to face off in a one-on-one battle, Saitama would easily win.
The sheer untapped power of Saitama from One-Punch Man beats Dragon Ball's Goku in terms of strength. There are two names repeatedly brought up when discussing the most powerful anime characters.