I would disagree. Magus is after Lavos for revenge, whereas Crono & Co. are after Lavos to save the world from injustice and terrible calamity. The quest Magus is on is completely different and far less worthy than the one the others are on. He may indeed fit with the description of a Byronic hero, but that doesn't make him not an antihero, because the difference between heroes and antiheroes depends very much on our conception of what a "hero" actually is, and in Chrono Trigger the concept is pretty typical moral fare. With that in mind: Antiheroes manage to advance heroic ends, without being heroes themselves. By having a grudge against Lavos and cooperating with Crono & Co., Magus was doing the right thing for the wrong reason. That's classic antihero behavior.
