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