Omni-Man. He's probably hundreds of years old and squashed 100s of "earths". He has a whole empire of people like him that sort of justifies what he's saying. And he's a trained fighter with a military mentality. Homelander is overpowered grown-child. He's also alone and there are other people who could probably combine to kill him. Also, Homelander was on some weak ass shyt where he wanted people to like him. And just comparing them as parents. Omniman literally sat up there like "i could just make another you, 18 years is nothing to me".
I think he said he’s over a thousand years old