By far the one achievement that will come from strictly luck. When you begin the 2nd mission, just walk over and climb the fence. Don't wait for anyone to move, just get up there as soon as you get to it. Then, climb back down. Back elbow one of the goons, both of them have dynamite, so it doesn't matter which one. As soon as it drops run over to it and just stand there. BOTH goons will come and stand by you. DON'T interact with either one, just stand there. If one starts to punch you or anything, just take it, as they both will die in a matter of 2 seconds. Even if you get kicked into the hole, both goons will die. This works 4/5 times, as I got my achievement, and tested it to make sure that it worked.