Yo I agree, it’d take a new level of connection and understanding to properly train and bond with a legendary. I dont have a degree in fanfic writing, but here’s a brief something: Sans was very patient and refrained from seriously damaging it, only enough to prove that if he wanted to catch Articuno, he could. He believed not all pokemon, especially legendaries, needed to be bound by anything, that sometimes its better to let them choose you instead of the other way around: “doesn’t matter how strong my pokemon are, your choice is relevant too. if you don’t feel like hangin around a lazybones like me, then hey, i wont force ya. freedom is cool too, and you should be able to enjoy it as long as ya want.“ This surprised Articuno, since other trainers who wanted to capture it intended to heavily injure it until they were sure it couldn’t escape. So after about a week later, it showed up at the skelebros house one night. Sans didn’t even have to ask. They stared at each other for a few moments before he threw a pokeball and watched as Articuno, healthy and with plenty of HP left, allowed itself to become his. Picking it up, he whispered, “welcome home, buddy.”