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