In this video guide I will show you how I killed a cloaked Shrouded enemy. Now this achievement can be a little luck based depending on how you go about it. First you will need to find one, they will be in some higher leveled areas for one. Another spot is while doing the mission The Signal for Marshall. There will be other locations as well throughout the game. You will notice they wear full body armor.They also have what appears to be night vision but with yellow eyes and wear some kind of powered back pack.
One of the easiest ways you might find is to have the rocket launcher and try to wait them out to go invisible and blast him to guarantee a one shot kill. Otherwise find some other weapon that might do a one hit kill. Rockets from the Phoenix might do the trick as well. You could also try and spam grenades in a horde of them and hope one goes invisible at the right time. Or last but not least you could get lucky like me and pop out shot one in the head with the assault rifle and get the achievement. Once the kill counts while they are invisible the achievement will pop.
Now I am curious how many people got this achievement in different ways so let me know in the comments.