Here is the full list of all 57 Star Wars Knights of the Old Republic II: The Sith Lords achievements.
Complete the game on the Dark Side
Have your character replace any of the Sith Lords on the main menu screen.
Acquire all Dark Side Powers.
Kill all the Jedi masters
Side with Vaklu on Onderon
Break Hanharr's spirit
Learn how to kill Jedi from HK-47
Deduce G0-T0's identity
Recruit Hanharr
Change your mind about siding with the Settlers at Khoonda
Reduce a companion's Influence to zero.
Recruit the Disciple
Learn Moving Meditation
Reach maximum Dark Side points
Destroy Peragus Astroids
Kill all Sith troopers before they can board the Ebon Hawk
Complete the game on the Light Side
Defeat Sion
Reach Player Level 30
Claim Darth Nihilus' mask.
Defeat Nihilus
Have 30 points in Demolitions.
Have 30 points in Stealth
Have 30 points in Treat Injury.
Have Persuasion over 30
Acquire all Light Side Powers
Install HK-47's unique module
Side with the Queen on Onderon
Win a Pazaak game with a full board
Fill the Party Selection screen
Complete the Mandalorian Battle Circle
Side with the Settlers at Khoonda
Get the named Lightsaber crystal
Flee Korriban after fighting Sion
Get this by starting the "Trapped" Quest on Korriban.
Loot a body on Korriban
Teach the Handmaiden the ways of the Force.
Listen to HK-47's definition of love.
Repair the damaged droid on the Ebon Hawk
Gain a Prestige class
Contruct your first Lightsaber
Convince Vogga the Hutt to sell fuel to Telos.
Recruit Mira
Have 30 points in Repair.
Have 30 points in Computer Use.
Beat the champ on Nar Shadaa
Convince the "champ" to lose the game without playing.
Learn Force Sight
Collect 10,000 credits
Recruit the Handmaiden
Reach maximum Light Side points
Complete the Handmaiden Battle Circle
Get your first Dark Side points
Let the Sith destroy the Peragus Asteroids
Dance for Vogga
Get your first Light Side points
Complete the Prologue