A guy said that Kratos can destroy many universes and is able to destroy the sun with one hit. Is this really true in the game?
Well, first of all, he did not destroy the sun, but god of the sun.
Helios is the God of The Sun and Guardian of Oaths. He is a major antagonist in God of War III. Helios is one of the strongest Gods, since he is the sun itself. In the third game, Kratos kills Helios by ripping his head off, causing the sun to be blocked by dark clouds, and an endless torrent of rain to pour down.
Also, he is not the destroyer of universes, but worlds.
Kratos: "By the Gods, what have I become?" Grave Digger: "Death. The destroyer...of worlds"
After battling Thanatos he puts Deimos, his brother, in grave. He attempted to kill himself at the bluffs, but ultimately relented, asking himself what he had become. The Grave Digger, who had been close by, revealed he had become "Death, the Destroyer of Worlds", before vanishing.