20. Sinistar (Sinistar)
https://www.youtube.com/watch?v=cLnsDr2WDOk Sinistar's main antagonist is a one-hit killer of a spaceship that is also shaped like a terrifying skull, backed by an utterance of some truly harrowing taunts that urge you to get the heck out of there. Sinistar's signature howls and one-liners have become a part of the pop culture lexicon, making him one of the most famous boss battles of all time. But if you take a look at the actual battles with Sinistar that you get involved with, you'll begin to see there's more to this fight than simply pelting him with enough damage to end his pitiful life. Your creation of the Sinibombs that are actually capable of killing him by shooting planets scattered around the area, it's all wonderfully exciting and the increase in challenge with each level is an absolutely perfect design.