Percy Jackson
Ares: The god of war dislikes Percy. His hatred for Percy only intensifies when Percy defeats him in a duel in The Lightning Thief. It is dangerous for Percy that they are on bad terms because Ares, being the god of war, thinks highly of revenge and is quite violent. Ares puts a curse on Percy, saying that when he needs his sword the most, it will fail him. He only goes along with granting Percy godhood because he can fight him as many times as he wants and Percy will just keep coming back.