So you want us to post how you did? Okay?
The Sith Emperor is the emperor of the Sith Empire.
http://www.starwars.com/databank/Sith_Emperor
#1 Is the Sith Emperor really unstoppable?
1. Nope. He was stopped mostly by one Jedi Knight who brought millennia of planning to ruin in a few months. Thousands of years of prep ending in failure. However, a few days of planning lead to him killing an entire council at once. He's power is too inconsistent to judge.
2. A weapon called a Lightsaber and a Ceiling crushed him easily without him being able to respond.
The Emperor lies beaten at your feet. For all his power, he was no match for you.
This statement shows that Vitiate actually was at full power and still couldn't fight the Hero. This also shows that the HoT is better than infinite potential, which Vitiate is above, having beaten Revan.
#2 Did Vitiate do anything note worthy of his own power?
My life spans millennia. ....A day, a year, a millennium—it matters not. I hold the patience of stone and the will of stars."
This shows that not only was Vitiate prepared to wait thousands of years to carry out his plan, but that the amount of time would not even matter. As none of his plans were fulfilled, it's obvious that Vitiate could not affect the galaxy beyond his own planet.
Also notice that all of the major victories for the Sith came from people other than Vitiate.
#3 Could Vitiate even destroy himself?
On Voss, it's showed that Baras, although a powerful sorcerer and Dark Side user, was able to bound the Emperor without him being any the wiser. Even then he needed an untrained Sith Lord to kill even himself.
CONCLUSION for Vitiate
He is nowhere near as competent as he claims to be, and on some occasions even admits his own weakness. There for he is not all powerful, nor is he able to actually destroy the galaxy.
Is this how we're supposed to post, LeGenD?