he claims he was betrayed but his is not so bitter
Perseus Jackson preaches of betrayals. He does not realize how many he has betrayed himself.
He promises her: I'll try to free you. He promises her freedom from curses and freedom from confinement — he does not deliver.
Percy claims that the gods did not deliver, that he'd asked them. But everyone knows the gods are not beholden to any promises. What happens to them if they break an oath on the Styx? Nothing.
Calypso is always written off. She does not know how to wield a knife to fight. People whisper of her weakness — she needed a man to get her off that island, how dependent!
But Calypso can heal. Sometimes she holds lives in her hands. Calypso can choose what to do with them, and those who have wronged her will feel the fury of her curses and they will feel the fury of her gentle healing hands.
She knows he has been through a lot. She acknowledges it. She is still resentful.
Luke Castellan was his major betrayal. Perseus Jackson claims he was betrayed, yet his is not so bitter as hers. He was not very close to Luke Castellan. Passing acquaintance.
Calypso got a promise. Calypso got a broken promise. Calypso got shattered glass.
The shards of the glass sometimes still prickle her feet and leave trails of blood wherever she walks. She cannot erase them or wash them away. The blood is like her bitterness.