The room leading up to Giygas is a vagina and the Devil's Machine is a cervix. Giygas' dialogue was based on rape; its lines come from the victim. You went back in time to when Giygas was more vulnerable. You went to abort a fetus. Giygas wasn't evil during that fight.
"You cannot comprehend the true form of Giygas' attack!" This isn't because it is immense evil, but because it was only attacking to protect itself. It showed Ness in the Devil's Machine to try and tell him they could be friends. Pokey calls it pure evil, but every word out of his mouth in the entire game is a lie.
|Left: Devil's Machine. Right: Giygas, possibly after winning the battle.|