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 Dark Side
Have your character replace any of the Sith Lords on the main menu screen.
Reach Player Level 30
Acquire all Dark Side Powers.
Kill all the Jedi masters
Side with Vaklu on Onderon
Learn how to kill Jedi from HK-47
Reduce a companion's Influence to zero.
Reach maximum Dark Side points
Recruit the Disciple
Deduce G0-T0's identity
Break Hanharr's spirit
Recruit Hanharr
Complete the Handmaiden Battle Circle
Destroy Peragus Astroids
Complete the game on the Light Side
Defeat Sion
Claim Darth Nihilus' mask.
Defeat Nihilus
Have 30 points in Stealth
Have 30 points in Demolitions.
Have 30 points in Treat Injury.
Teach the Handmaiden the ways of the Force.
Acquire all Light Side Powers
Install HK-47's unique module
Side with the Queen on Onderon
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
Side with the Settlers at Khoonda
Change your mind about siding with the Settlers at Khoonda
Contruct your first Lightsaber
Have Persuasion over 30
Get the named Lightsaber crystal
Gain a Prestige class
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.
Learn Force Sight
Reach maximum Light Side points
Have 30 points in Repair.
Have 30 points in Computer Use.
Collect 10,000 credits
Learn Moving Meditation
Recruit the Handmaiden
Get your first Dark Side points
Win a Pazaak game with a full board
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