Totally Accurate Battle Simulator

Once you have all the units unlocked go to the workshop. In battles search "Achievement 1 win a battle with each unit" by GeniusLi. Click the "install and subscribe" button. Then go to custom content on the main menu and play that level. Every unit from all the factions that have achievements will automatically be placed with one enemy unit. In one second it will die and all the achievements relating to placing faction units down will unlock.