Ever-watchful Xbox 360 Achievements has dug up what it says is the list of cheevs for BioShock 2; there are 50 for the standard total of 1000 gamerscore, and a goodly number of them are secret achievements.
Here's the full list. It rates a standard spoiler-alert warning but, going through this, the descriptions don't seem to give up many details of the singleplayer campaign. Be sure to check the link to see the achievement icon art.
• Bought a Slot (5 points)
Buy one Plasmid or Tonic Slot at a Gatherer's Garden.
• Max Plasmid Slots (10 points)
Fully upgrade to the maximum number of Plasmid Slots.
• Upgraded a Weapon (10 points)
Upgrade any weapon at a Power to the People Station.
• Fully Upgraded a Weapon (10 points)
Install the third and final upgrade to any of your weapons.
• All Weapon Upgrades (20 points)
Find all 14 Power to the People weapon upgrades in the game.
• Prolific Hacker (20 points)
Successfully hack at least one of every type of machine.
• Master Hacker (20 points)
Hack 30 machines at a distance with the Hack Tool.
• First Research (5 points)
Research a Splicer with the Research Camera.
• One Research Track (20 points)
Max out one Research Track.
• Research Master (20 points)
Max out research on all 9 research subjects.
• Grand Daddy (25 points)
Defeat 3 Big Daddies without dying during the fight.
• Master Gatherer (30 points)
Gather 600 ADAM with Little Sisters.
• Fully Upgraded a Plasmid (10 points)
Fully upgrade one of your Plasmids to the level 3 version at a Gatherer's Garden.
• All Plasmids (20 points)
Find or purchase all 11 basic Plasmid types.
• Trap Master (15 points)
Kill 30 enemies using only Traps.
• Master Protector (15 points)
Get through a Gather with no damage and no one getting to the Little Sister.
• Big Spender (15 points)
Spend 2000 dollars at Vending Machines.
• Dealt with Every Little Sister (50 points)
Either Harvest or Save every Little Sister in the game.
• Against All Odds (30 points)
Finish the game on the hardest difficulty level.
• Big Brass Balls (25 points)
Finish the game without using Vita-Chambers.
• Rapture Historian (40 points)
Find 100 audio diaries.
• Unnatural Selection (10 points)
Score your first kill in a non-private match.
• Welcome to Rapture (10 points)
Complete your first non-private match.
• Disgusting Frankenstein (10 points)
Become a Big Daddy for the first time in a non-private match.
• "Mr. Bubbles– No!" (20 points)
Take down your first Big Daddy in a non-private match.
• Mother Goose (20 points)
Save your first Little Sister in a non-private match.
• Two-Bit Heroics (10 points)
Complete your first trial in a non-private match.
• Parasite (10 points)
Achieve Rank 10.
• Little Moth (20 points)
Achieve Rank 20.
• Skin Job (20 points)
Achieve Rank 30.
• Choose the Impossible (50 points)
Achieve Rank 40.
• Proving Grounds (20 points)
Win your first non-private match.
• Man About Town (10 points)
Play at least one non-private match on each multiplayer map.
• Two Secret Achievements worth 5 points.
• Two Secret Achievements worth 10 points.
• One Secret Achievement worth 15 points.
• Six Secret Achievements worth 20 points.
• One Secret Achievement worth 50 points.
• Two Secret Achievements worth 25 points.
• One Secret Achievement worth 100 points.
BioShock 2 Achievements List [Xbox 360 Achievements via HBG]