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