Saitama

Saitama is the titular One-Punch Man and the strongest character in the series. So far, no enemy has been able to injure him in any way, and almost no enemy has been able to survive a single earnest punch from him. A few enemies have survived punches from him, such as any human he has struck (whom he restrains himself against) and Boros, whom Saitama empathized with and held back against so as to give himself and Boros a satisfying and stimulating fight.