Livelock

1: alloy spider lvl 1-1
2:protected lvl 1-10
3:spider host lvl 2-1
4: wasps lvls 2-1 and 2-3
5 Ivan lvl 3-1 during the waves at the end of the level don't kill the big Ivan till the normal ones spawn one at wave 1 and at wave 3
6: siege breaker lvl 2-6
7: gaster lvl 2-3
8: forsaken lvl 1-3

UPDATE: I've been informed that the game has been updated to include a tracker for your enemy kills.

This really isn't a solution, it's more just giving you an idea of what this achievement entails.

When you start the game, every new enemy you kill will have a card pop-up on the right side of your screen showing a picture of the enemy and saying "data card unlocked". The first enemy you kill (likely the spiders in 1-1) will unlock the Script Kiddie achievement.

That first card will likely be 1-25 kills on those spiders (I don't remember the exact number). Each enemy type in the game has a data card with a required amount of kills. They range anywhere between 25, 50, 100, or 200 kills.

A Master Data card is simply a completed data card. So once you kill, for example, 25 spiders on 1-1 that card is now a Master Data Card and you will unlock the 1337 h4x0r achievement. To get ALL Master Data Cards you have to complete the kill requirements for every enemy type.

If you didn't notice this when you first played the game, play on a new account to see what I'm talking about.

A few tips:
- The data card will appear on the right side of your scree (above your top gun, below your score)
- Kills count for everyone in co-op but I'm not sure if range is a factor
- Chapter 3-1 has an enemy type at the very final battle of the mission that you might be missing
- Chapter 3-2 has Drones and Hammer enemies that you may be missing
- Chapter 1-1 has tiny spiders that you may be missing
- Chapter 2-5, you have to kill the Atlas Boss 25 times (credit to Clad Master)
- Chapter 2-6 you have to kill the Siege Breakers (large, walking tanks when you're defending)
- Kills most likely count across all characters but I'm not 100% on that

From I Am Cully:

Lev 1-1
Alloy Spider (tiny bugs) - 100
Shank (small black doggies) - 200
Eliminator (human shape with 1 machine gun arm) - 500

Lev 1-2
Scourge (whip/claw ground guys) - 200

Lev 1-3
Forsaken/Parallax (dome head guy) - 50

Lev 1-4
Shatter Cannon (invisible sniper) - 50

Lev 1-5
Mongrel (explodey dogs) - 100

Lev 1-6
Ravager (turret/mortar guys) - 50
Dampener (purple monk looking things with dress) - 100

Lev 1-8
Pounder (beefy guys that smash you with big fist) - 50

Lev 1-10
Protected (standing machine gun turret guys) - 50

There is no way to track these kills in-game. Good luck!

Just to add to other solutions and the vague update by Mr BlackMagik. Yes, you are able to track your progress for these kills and how many you need or have left.

If you're on the title screen go to DATABASE and click you're in. This tracks all the kills of enemies you need in the "The Corrupted" tab, which is the default as soon as you open up database. It also tracks and has its own tabs for "Audio Logs", "Weapons", "Functions", and "Achievements".

The gold border means its completed. The blue border means you still need kills.

If you click on a blue border card it gives a brief description of what "the corruption" is and how many kills you have and how many total. For example: alloy spider 80/100.

If you click on the gold ones it says (mastered) plus however many killed so far.

Have a Blessed day.