You must complete the research tracks on the following enemies in a single playthrough. You will know that you have completed a research track when you can't research a type of enemy anymore, and you have received a gene tonic as a reward for your research.
- Big Daddies: This includes all the various types of Big Daddies you encounter escorting the little sisters, NOT the Alpha Series.
- Leadhead Splicers: These are the basic Splicers you see walking around carrying guns.
- Thuggish Splicers: These are the basic Splicers that carry melee weapons, like pipes. It's best to max this research track out as soon as possible, as these don't appear very often (if at all) towards the end of the game.
- Spider Splicers: These are the Splicers that jump around on the walls and throw what look like hooks at you. They start appearing in the Siren's Alley level and feature fairly frequently from then on.
- Big Sisters: Big Sisters show up after you've gathered or harvested all the Little Sisters in a level, and also in some story driven events. It is of the utmost importance that you research every one you possibly can, else it is unlikely that you will complete their research track. I did not complete their research until the final area of the game.
- Brute Splicers: These are the hulking splicers new to BioShock 2. There are plenty of them towards the end of the game, and as such it shouldn't be hard to research them completely.
- Houdini Splicers: These are the splicers that teleport around and launch fireballs at you. They begin appearing in Dionysus Park, but you will find plenty of them from Fontaine Futuristics and onwards.
- Security: Bots, Cameras and Senty Guns all count to the same research track and there are plenty of opportunities to reach them. If worst comes to worst, you can try to hack a vending machine and consistantly fail by landing on the red zone, which will triggeer a security alarm and summon bots for you to research.
- Alpha Series: These are the prototype Big Daddies you encounter from Fontaine Futuristics onwards. There are lots and lots of them in the last few levels and should not be difficult to complete.
Please note that you can only research each individual enemy once. Some general tips for researching are:
1. Use a variety of elemental plasmids on them. Each different type of elemental plasmid you use on an enemy adds an additional 100 research points.
2. Obtain and use the Keen Observer tonic in the area prior to meeting Grace. It'll make your research worth more.
3. Obtain and use the Extended Reel gene tonic in Dionysus Park. It'll make your research last longer on enemies, allowing a much higher number of points to be obtained on enemies which take a lot longer to kill, such as Big Daddies and Big Sisters.