Quote from rollawaythedew»
Anything to help a fellow Minecrafter!
I wouldn't say that any of the bosses are villains though, a villain is a character whose actions are important to a plot, Minecraft has no set story! Perhaps antagonist considering the Enderdragon's minions are constantly opposing the player and the Wither is the Nether's boss, or you could go simply with good ol', "boss".
Even though Minecraft has no story, I would still consider the Enderdragon and Wither villains as much as bosses. I mean there would be a reason they are bosses; who else rallies all the Endermen to the Overworld, and The Wither could explain the ruined Nether Fortresses.