Splatterhouse

Ok I really didnt find the above solution very informative so I will tell you the easiest method, learn the grapple technique that allows you to rip off enemies arms you will use this often, this will give you a free arm now smack away with it and the achievement is yours. Another way to quickly get it at teh beginning use the machete this allows limb removal

Just rip off an enemy's arm and kill him with it. You should get it near the beginning of the game when you do an arm rippoff splatterkill. So easy.