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