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