After Athena pointed out Medusa to Perseus, he knew what to do. Perseus slayed Medusa with no hesitation. He cut off her head without turning to stone himself.
The Road Back
There were three gorgons in a formation in a formation. According to advice given by Hermes,Medusa was the one in the middle. Perseus used the mirror in the shield given by Athena to see her without looking directly at her..Ultimately, Perseus cut off Medusa's head and returned it to Polydectes.
Perseus then traveled back home. Once he arrived, Polydectes confronted him and was very surprised at his return, considering that the trip was one of a deadly manner. Perseus soon got the memo that the trip was meant to get rid of him and Perseus marveled at the fact that he made it, but soon got angry.
Return with the Elixir
On the trip back to return Medusa's head to Polydectes, Perseus encountered a sea monster. He killed the monster to save his future wife, Andromeda. When finally back to the island, Polydectes denied that Perseus actually slayed Medusa. When he pulled out her head to prove it him wrong, Polydectes instantly turned to stone.
King Acrisius had been attending games in a nearby city. The same grandfather who put Perseus and his mother in a trunk and into the sea. Hearing of his grandfather's appearance in the nearby city, Perseus took part in the games.
At the games, Perseus took his turn at throwing the discus. When leaving his hand, an unexpected wind shot it towards King Acrisus, a spectator, and killed him. This fulfilled the prophecy at the oracle at Delphi.