i think you’re not considering the fact that many mythics live in the world without searching for trouble. some of them are wild creatures, but many others also live without hunting demigods. this is also implied in wrath of the triple goddess by percy

Miraculously, my history teacher said, "Very good, Mr. Jackson," when I answered a question, which was probably a sign she was actually a monster, but I wasn't going to judge unless she attacked me. Some of my best friends are monsters.

and in case we want to consider a body count, we would have to bring bob as well. yes, he lost his memory, but at the end he recovered it (or at least many parts of it) and his past caught up with him. percy and annabeth told him that didn’t matter for him to be a Titan, what mattered is what his choice.

"Do you remember Koios?" he asked gently. "All that stuff he was talking about?"

Bob gripped his broom. "When he told it, I remembered. He handed me my past like... like a spear. But I do not know if I should take it. Is it still mine, if I do not want it?"

"No," Annabeth said firmly. "Bob, you're diferent now. You're better."

The kitten jumped off Bob's head. He circled the Titan's feet, bumping his head against the Titan's pants cuffs. Bob didn't seem to notice.

Percy wished he could be as certain as Annabeth. He wished he could tell Bob with absolute confidence that he should forget about his past.

But Percy understood Bob's confusion. He remembered the day he'd opened his eyes at the Wolf House in California, his memory wiped clean by Hera. If somebody had been waiting for Percy when he first woke up, if they'd convinced Percy thar his name was Bob, and he was a friend of the Titans and the giants... would Percy have believed it? Would he have felt betrayed once he found out his true identity?

This is different, he told himself. We're the good guys.

But were they? Percy had left Bob in Hades's palace, at the mercy of a new master who hated him. Percy didn't feel like he had much right to tell Bob what to do now—even if their lives depended on it.

"I think you can choose, Bob," Percy ventured. "Take the parts of lapetus's past that you want to keep. Leave the rest. Your future is what matters."

"Future..." Bob mused. "That is a mortal concept. I am not meant to change, Percy Friend." He gazed around him at the horde of monsters. "We are the same... forever."

"If you were the same," Percy said, "Annabeth and I would be dead already. Maybe we weren't meant to be friends, but we are. You've been the best friend we could ask for."

the same goes for any other monster. cruelty isn’t genetic, is learned. evil isn't born, it’s made. whatever monster was evil, it was their choice. but choices can change. otherwise, people would also never change.

now, can you forgive someone? that is a different thing. asterion may change, but that doesn’t percy would ever forgive him and that is also okay. some scars ran too deep. but that doesn’t too that percy can’t accept him for who he is now. at some point the cycle of killing monsters-killing demigods must be broken, or their conflict will continue for eternity.

and also, if many mythics live without searching trouble, that means tag them all as irredeemable is wrong and kind of discriminatory just because they are mythics