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