Rathalos is a boss in both World of Light and classic mode. I thought he was from Xenoblade Chronicles (I’ve never played it) but he’s actually from the Monster Hunter games. Monster Hunter is really popular in Japan so I’m not shocked to see him show up.
He’s one of the tougher bosses too. He flies around too often, and he’s pretty annoying to try to hit.
He’s also got plenty of fire to make your battle miserable.
But he can be somewhat easily slain. He was one of my least favorite bosses in the game however.