Game: The Super Mario Brothers series (1985-2012)

How intimidating can a boss be when a diminutive plumber keeps beating him? But, nonetheless, Bowser (aka King Koopa) still finds a way. Reappearing throughout the series, Bowser grows in difficulty and power. He starts out throwing fireballs and bringing the ceiling down on you. Eventually, the mutant turtle upgrades to larger than life proportions and abilities including flight, using helicopters and staring in that really bad Mario Brothers movie. Bowser is one of the few bosses that upgrade as consoles and games evolve