Originally posted by NewGuy01
What leads you to believe it's combat applicable? I daresay that if he can pull that kind of stunt on a whim, he would have just done so the moment he arrived on Ziost.
Recall this?
He allowed their plan to play out, but when they gathered to confront the Emperor, his punishment was swift and devastating. Eleven members of the Dark Council died in a sudden flash on the steps of the Citadel. The last member Darth Lokess, disappeared forever, though for some centuries some claimed her screams could be heard from the bowels of the Citadel.
Taken from Star Wars: The Old Republic: Encyclopedia
It is important to understand the story before jumping to conclusions. Vitiate arrived on Ziost and began to possess individuals across the planet to utilize them for murder and chaos. In this manner, Vitiate was able to grow further in power by drawing on the chaos and deaths he caused (i.e. Force Drain). The Protags arrived and attempted to stop Vitiate but failed. More importantly, Vitiate became so powerful from the chaos he caused on Ziost, that he ravaged the entire planet afterwards. The Protags evacuated before they would be consumed.
Obsessed with achieving immortality, the Sith Emperor has targeted his own former subjects on the planet Ziost, with every death seemingly extending his dark power. Speaking through those he's possessed, he controls powerful pawns like Master Surro, the leader of a team of elite militarized Jedi known as the Sixth Line.
Taken from Star Wars: The Old Republic: Rise of the Emperor
Vitiate's showings in Ziost are definitely combat-applicable.
If Vitiate wants to kill someone, he does. Similarly, if he wants to spare or toy with someone, he does this too.