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