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