He is the first of what would become a long line of really tough boss characters to fight in the Final Fantasy legacy. He forges an unholy alliance with the Four Fiends and begins a loop lasting two thousand years that makes him nearly immortal. He also transforms into Chaos, the ultimate evil boss. With big wings and a host of tough attacks, he was the first guy in the series to really drive us nuts. Though this boss may not have had the graphical intensity of the bosses and mega-bosses that would follow, the fact that he gave us so much trouble in such an early title is seriously mind-boggling and the reason that he receives the tenth spot on this list.