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