Saitama faces Boros, a galaxy-conquering alien who, like Saitama, is bored because he is too strong.
King uses a megaphone to bait the Elder Centipede into a trap, allowing Saitama to finally arrive and disintegrate it in one blow. Season 3, Episode 12: " The Ultimate Lifeform " One Punch Man Episode 12
This episode is widely considered the "gold standard" for the series. Saitama faces Boros, a galaxy-conquering alien who, like