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