[i]Coolest[/i] doesn't always mean most powerful. The last two can most easily be swapped with at least five others. While there are only seven options, Vitiate lived for millenia and singlehandedly created a massive Sith empire in secret, ensuingly orchestrating the devastating Mandalorian war and almost wiping out all of the Jedi, and Nihilus is simply darkness encased in an awesome mask. EDIT: Obviously should have incorporated Maul.