Feel bad for Genos. When will he catch a break?
I think Saitama's Serious Punch was just misleading. He may just been excited about the strength of the Elder Centipede before he attacked, because he looked disappointed after he punched it.
I only think the serious punch was necessary for the sheer size of him. A normal punch may not have destroyed every single bit of him.
What do you mean? King told him he couldn't send the centipede flying at the city. So he used a serious punch to completely destroy it and avoid collateral damage.
I thought the serious punch was also because he was still pissed off after getting owned in video games by King all day. King even mentions it, they're hilarious It might be why he waited til the last second, to scare King a little bit haha