Use Anakin Skywalker as your example, he became a sith to save Padme, but his path eventually blinded him, and many deaths at his hands. The Game will feature this in it, as you go too dark, your actions will be with more fury, to the point your charather will attack enemys instantly.
But I only heard that from another guy.

We have to study all its aspects ( of the force )

"Every Jedi is stronger with the powers... every power is available to achieve... the way of using these powers is important" - KYLE KATARN
Using the dark or light side of powers in good way, to protect others and fighting the evil... This is what Kyle Katarn wanted to say.

So I don't choose any side. I just can't do that. I would be stronger if I used all powers available to achieve.

I am like Kyle Katarn. He was a sith, he felt to the dark side, but then he redeemed himself... He is not a true Jedi.
Desann said that to him and Kyle confirmed that...

this is the difference when you look at Revan and malak. Malak was impatient to have all the powers, he couldnt control his urge like many other siths. Revan was patient and was able to judge what was right or not. Malak would try to find someone to kill. Like on taris when he destroyed the entire city just to kill Revan.

I read somewhere ( il try finding a link ) that the siths were like revan before he vanished in the unkown regions. it is after his fall that a fallen jedi decided to push the power and limits of the siths. He thought the could be more powerful if they killed and destroyed everything they could to rule people through fear.

Ps: this is the reason why revan was on the light side, turned to the dark side went back on the light and (depending on your ending) turned back to the dark. Because he was sort of in between like kyle though darker

And yes, Revan did love Bastila Shan, but they never showed it for the Teen Rating, but you can see it in a mod.