I guys this achievement is so hard but I found a solution and you can even do it on solo mode here it is just watch this https://www.youtube.com/watch?v=DucK470dSNM but map c1m4_atrium teamscavenge doesnt work anymore but map c4m1_milltown_a teamscavenge works when you type it on the console and thats how i got the achievement so got luck on getting the achievement and please do comment down below if it work on you guys  thanks guys :)