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