Tbh, Athena got off really easy there. She could've suffered more, but I guess her pride as the goddess of wisdom didn't allow her to easily fell against the wishes of her enemy and choose the easiest way.
Hey author for training why not make ghidorah go the saiyan usual training?
He can shoot himself or place himself under gravity and then excersise and then shoot lightning and other elemental magics to himself to gain inmunity or at least a lot of pain tolerance