Here is the full list of all 57 Star Wars Knights of the Old Republic II: The Sith Lords achievements.
Change your mind about siding with the Settlers at Khoonda
Complete the game on the Dark Side
Have your character replace any of the Sith Lords on the main menu screen.
Kill all the Jedi masters
Side with Vaklu on Onderon
Listen to HK-47's definition of love.
Break Hanharr's spirit
Contruct your first Lightsaber
Recruit Hanharr
Teach the Handmaiden the ways of the Force.
Recruit the Handmaiden
Destroy Peragus Astroids
Reach maximum Dark Side points
Complete the game on the Light Side
Defeat Sion
Claim Darth Nihilus' mask.
Defeat Nihilus
Side with the Queen on Onderon
Reduce a companion's Influence to zero.
Fill the Party Selection screen
Complete the Mandalorian Battle Circle
Flee Korriban after fighting Sion
Get this by starting the "Trapped" Quest on Korriban.
Loot a body on Korriban
Deduce G0-T0's identity
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.
Side with the Settlers at Khoonda
Recruit the Disciple
Learn Force Sight
Get the named Lightsaber crystal
Complete the Handmaiden Battle Circle
Win a Pazaak game with a full board
Get your first Dark Side points
Gain a Prestige class
Install HK-47's unique module
Learn how to kill Jedi from HK-47
Repair the damaged droid on the Ebon Hawk
Learn Moving Meditation
Let the Sith destroy the Peragus Asteroids
Kill all Sith troopers before they can board the Ebon Hawk
Dance for Vogga
Collect 10,000 credits
Acquire all Dark Side Powers.
Acquire all Light Side Powers
Have 30 points in Demolitions.
Get your first Light Side points
Reach maximum Light Side points
Have Persuasion over 30
Reach Player Level 30
Have 30 points in Stealth
Have 30 points in Treat Injury.
Complete the Prologue
Have 30 points in Repair.
Have 30 points in Computer Use.