Just one punch is all it'll take for Saitama to beat Goku. ... However, Saitama's strength is often undermined by fans when compared to Goku. For instance, yes, Goku is a Saiyan, an alien warrior race, who has the ability to enhance his strength by transforming into a Super Saiyan....
Knowing that she lacked the physical strength to beat someone like Doma (the second-strongest demon surviving under Muzan Kibutsuji), Shinobu allowed herself to be eaten by Doma to weaken him and allow a killing blow. This particular poison was so powerful that it actually melted Doma's flesh...