"Nobody's killing me now by fraud and not by force!"
In this line, Polyphemus is talking about Ulysses (who claimed his name was Nobody). He says that Ulysses tricked him instead of fighting him. Polyphemus also tells about how he once met a prophet, who told him about how he would be blinded by Ulysses. However, Polyphemus thought Ulysses would be "a handsome giant man...some fighter clad in power", instead he says Ulysses is "a dwarf, spineless good-for-nothing". These both show how the cyclops is disappointed that he is not defeated by strength but rather cleverness.