Another member of the Blizzard's universes, November "Nova" Terra is among the most lethal. Imagine this: your job as a government assassin is not only to take out notorious criminals like the terrorist "Jim Raynor", but also to take out the unruly Protoss, and colossal enemies like the Zerg Ultralisk. Sounds like a difficult job, right? Not for Nova.
As a Ghost operative, the Dominion Army is Nova's weapon. Her ability to call down nuclear missiles, Battlecruiser Yamato Cannons, and siege tank strikes puts her authority and destructive capabilities well beyond those of her predecessor, Sarah Kerrigan (when she was still a ghost that is). She also has the benefit of having a permanent cloaking generator, something that is only granted to the highest-ranking Ghost operatives.
That not enough to convince you? Well how about this: she is the only Terran Ghost known to mind control her opponents. That means no one is safe from her reign of terror.
With this stellar set of abilities, Nova Terra gets a well-deserved #4 slot on this list. Now if only she could get her own game...