Hi Guys,
here is my Solution for this Achievement. In the 4. Mission called Time and Fate you play in a short Sequence Raul Menendez.
In this short Sequence are 7 Brutalitys and you must Kill all involved Soldiers.
4 in the first Part of the Sequence then 1 in the "middle" and 2 at the End.
Regards
PS: sorry for my english, german :)