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