When in doubt, gas those suckers out with your own personal affliction of Toxic Damage for Toxic Weapon Kills in Modern Warfare 3‘s Zombie mode.
This is our full guide on how to get Toxic Damage Weapon Kills in MW3 Zombies.
Toxic Damage in MW3 Zombies explained
There are multiple ways to use Toxic Damage in MWZ and it’s not what you think it is. Toxic Damage is inflicted through the use of Experimental Gas and Brain Rot. While achieving Brain Rot is harder than unlocking Experimental Gas via the Armory Unlock, you still need to progress to level 25 to use the Armory Unlock Daily Challenges.
I found the Brain Rot and Cryo Freeze Ammo Mods in almost every match by completing Contracts and clearing Aether Nests and Strongholds (Infected and Mercenary). Be sure to loot all crystallized crates after clearing Strongholds and checking for these Ammo Mods inside Reward Rifts.
The Brain Rot Ammo Mod alongside all Ammo Mods lasts until the moment you exfil. With this in mind, you can easily complete camo challenges that require Toxic Damage simply by using the exfil method.
MWZ: How to get Toxic Kills for weapon camo challenges
Firstly, make sure that you are heading into the deployment with your relevant weapon needed for these Toxic Damage kills. In my case, this is the Striker 9. You must first reach the relevant camo challenge level to start farming Toxic Damage kills. Next, you can either place your bets on finding a Brain Rot Ammo Mod in Urzikstan or progress to level 25 to unlock Armory Upgrades and then complete five Daily Challenges for Elemental Gas permanent unlock.
You can begin getting Toxic Damage Weapon Kills once either method is achieved (Elemental Gas unlock or finding the Brain Rot Ammo Mod). If you safely exfil without using the Brain Rot Ammo Mod, you can craft it using the Acquisition Stash. Make sure that you have either the Elemental Gas in your tactical slot for your loadout before you deploy.
When you are in the game, all you need to do is equip either the Brain Rot Ammo Mod through the Acquisition Stash crafting or find it in loot caches and Reward Rifts, or the Elemental Gas. The Brain Rot Ammo Mod will not work on every zombie but it has a chance of inflicting the Brain Rot onto a single zombie for them to assist you temporarily in the fight. I have found that the Brain Rot zombie is capable of getting an average of three to five kills.
The Elemental Gas grenade deals Toxic Damage to any zombies within its radius. The problem with the Elemental Gas is that it does very minimum damage and has limited use within a single deployment. This means you’ll have to commit to multiple playthroughs to get the Toxic Damage necessary for your camo challenge.
I highly recommend the Brain Rot Ammo Mod as you can farm kills inside exfil hordes and repeat this for 20 minutes, rewarding you with a ton of Toxic Damage kills. You will still need to do multiple deployments but the Brain Rot is a far quicker method. Keep an eye on the ‘Brain Rot Kill‘ as an indicator for successful Toxic Damage Kills.