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