Nailz08341,872 Locked 10 Feb 2016 12 Feb 2016
For this achievement I used the character "The Captain" I used this character because you will unlock 3 types of infantry by level 5. Infantry is under the "Structures" tree when using earned modifiers in the Armory. You will accrue modifier points with each level gained playing the game. The three types of infantry are "Rifle Infantry", "Rocket Trooper", and "Tesla Trooper". I invested 2 points in each to ensure all abilities will be unlocked.
Once you have done this you can load up a "Solo" game. Select "Captain" as your character, and select "Level 2: Taswell's Theatre" on "normal", in "Campaign".
Update: Thank you "Sighris" he stated you can use your weapons and I tested this with another account to be 100% accurate.
When the level starts you will need to defend the base for 4 waves. Press the B button to choose your loadout. Select the weapons you want to use these will not affect the achievement. Next you need to select "Structures" and pick your 3 infantry types mentioned earlier. If you have a 4th structure you can select it, but it will not be used.
Here is the Infantry loadout Iused with abilities.
Rifle Infantry "Platoon" This deals increased damaged when near other infantry.
Rocket Trooper "Napalm Frags" Fire incendiary shells instead of rockets.
Tesla Trooper "Phoshorescence" Increases the fire rate of the Tesla trooper.
You will have $2,000 to spend when starting the level. Use the follow command after placing troops. Commands are given to infantry troops via the control pad. Use the right directional button on the dpad to select the "follow" option command. Since we are using the follow command place your troops where you like. I started by the right side but its up to you. I selected 3 Infantry, 1 rocket and 1 Tesla troop to start.
Wave 1: All enemies will come from the right entrance. This will be fast and easy, Kills enemies as needed. Your troops will follow you so stay near the enemies but out of the line of fire when possible.
Wave 2: All enemies will come from the left entrance you will have earned some money so add more troops I added one Rifle Infantry.
Wave 3: You will have earned a lot of money from clearing wave 2 so use it to buy 2 more Tesla Troopers, 1 Rocket trooper, and 1 Rifle Infantry. Enemies will come from both entrances so you will to hold your ground near the base. It's OK if the base takes some damage it just can't get destroyed.
Wave 4: final wave you will have a lot of money but will only be able to select 2 more Troopers, the game gives you a limit on how many structures you can use. I selected a Rifle Infantry, and a Rocket Trooper as my last two. You could swap either with a Telsa Trooper and probably be fine. Again enemies will come from both sides and be larger in numbers. Hold your ground near the base and move from side to side to clear them out as far away as possible. My base was at 25% health when wave 4 was finished, so there was plenty of room for error.
Good luck and let me know if if the guide does not make sense. It's pretty easy and you should be able to knock this out on your first try.
Thanks for the comment "Sighris"