I dunno, there's a scene near the end of the game that let your character act deliciously cruel, to the point of shivers.
SPOILERS COMING
---
I'd played the light-side path the entire game, paragon of virtue, etc. Just for fun, right before I had to decide either to continue do-gooding or to embrace my destiny, I saved. "Let's see what this dark side gig has to offer," I thought.
With my saber, now crimson (natch), humming away, I approached my party who, until that moment, thought I was more virtuous than Jesus and Superman combined. Mission, the runt, wouldn't accept I was who I claimed I was. I gave her a choice: embrace the path of hatred, or suffer by it. She chose.. poorly.
That, in itself, isn't the evil part. Anybody can kill an annoying blue girl. What was fun was how I did it. You see, I posed the "by my side or by my saber" choice to everybody, including the wookie Zaalbar -- Mission's life-long infinity-bestest friend in the universe -- who, as payment for saving his life, had sworn a wookie life-debt pledging himself to me until his death.
Oh, this is too perfect, you guys.
I looked Mission square in the eye, and ordered my Wookie to honor his sacred vow. I ordered him to murder his best friend in the world. And he did it. He bludgeoned the turncoat into a blue pudding with her own dainty little arms.
He hated me for it, naturally. More than anything in the world, he hated me. I loved him for it. His primal fury. His unfathomable sorrow. I drank from him, as if he were a fountain. It satiated me.
I thanked him.
---
Now that's some good evil!