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