Zarra

From the Star Wars universe. Set right after Episode I: Phantom Menace. Zarra is a Zabrak Sith, younger sister of Darth Maul. She is actually even more powerful than Maul himself. She hates Obi-Wan Kenobi for killing her brother (she doesn't know Maul actually survived, got the droid legs and is in hiding somewhere; neither does Kenobi, of course). You are Obi-Wan Kenobi. You are walking alone one evening, on some desolate Outer Rim planet, and Zarra ambushes you, looking for revenge.