Here is the full list of all 13 Easy Red achievements.
Kill 10 soldiers
Learn how to play
Take Easy Red sector.
Share your creation on the workshop.
Survive from 25 germans on survive mode.
Survive from 100 germans on survive mode.
Take Marville back
Kill 100 soldiers
Kill 1000 soldiers
Survive from 250 germans on survive mode.
Kill an enemy while in underwear
Survive from all germans on survive mode.
Nobody knows how to unlock this.