For a quick and easy unlock, the method that Ditto51 outlines for "Put Up Your Dukes" is very good.
The method he outlines can be seen directly by the link below. In short summary, 2 controllers, Forge, Nebula map, commence beating down your "opponent". Using his outline, this will unlock in 15-20 minutes tops.Solution for Put Up Your Dukes in Halo: The Master Chief CollectionAll credit goes to Ditto51 for this method
, which can be easily and effectively applied to the Dim Mak achievement. If Ditto51 wants to post his own solution here to his credit, I will gladly delete this one to avoid too much repetition.