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