The question of whether Saitama can beat Mastered Ultra Instinct (MUI) is a highly debated topic among fans of anime and manga. To answer this question, we first need to understand who these characters are and what their abilities are.

Saitama is the main character of the anime and manga series “One-Punch Man.” He is a hero who has trained his body to the point where he can defeat any opponent with a single punch. His strength, speed, and durability are all at levels that are far beyond those of normal humans or even most other anime/manga characters.
On the other hand, Mastered Ultra Instinct (MUI) is a technique used by Goku in the anime and manga series “Dragon Ball Super.” It is a state of being where the user can move and react without thinking, allowing them to dodge attacks and strike back with incredible speed and power.
So, can Saitama beat someone who has achieved Mastered Ultra Instinct? The answer is not as simple as a yes or no.
First, let’s look at Saitama’s strengths. As mentioned earlier, Saitama’s strength, speed, and durability are all at levels that are far beyond those of most other anime/manga characters. He has been shown to effortlessly defeat opponents who would be considered impossible for other characters to defeat. For example, he defeated Boros, a villain who was said to be capable of destroying planets, with a single punch.
However, Saitama’s greatest strength is also his greatest weakness. His overwhelming power means that he does not have many opportunities to use his skills in combat, as he can defeat most opponents with a single punch. This means that he has not had much opportunity to develop his fighting skills, which could put him at a disadvantage against someone who has achieved a technique like MUI.
Now, let’s look at MUI. The technique is achieved through intense training and mastery of the body’s movements. In this state, the user’s body moves without thinking, allowing them to dodge attacks and strike back with incredible speed and power. However, using MUI requires a tremendous amount of energy, and the user can only maintain the state for a limited amount of time.
Given the above, it is possible that Saitama could defeat someone who has achieved MUI. His overwhelming strength and durability would make it difficult for his opponent to land any significant blows on him, and his own punches could potentially defeat his opponent in a single hit.
However, it is also possible that Saitama could be defeated by someone who has achieved MUI. As mentioned earlier, Saitama has not had much opportunity to develop his fighting skills. This could put him at a disadvantage against someone who has achieved a technique like MUI, which requires a high level of skill and mastery.
Additionally, it is worth noting that Saitama has never faced an opponent who has achieved MUI. This means that we cannot say for certain how he would fare in such a battle. It is possible that he would be able to overcome the technique with his overwhelming power, or he could be caught off guard by his opponent’s incredible speed and reflexes.
In conclusion, the question of whether Saitama can beat someone who has achieved Mastered Ultra Instinct is not a straightforward one. While Saitama’s overwhelming strength and durability make him a formidable opponent, his lack of fighting skills and experience against opponents with similar abilities could put him at a disadvantage. Ultimately, the outcome of such a battle would depend on a number of factors, including the specific abilities of both characters and the circumstances of the battle.