-First you need to be Level 7 to unlock JASON PART 7 He has the Machete as his weapon which is a requirement for this achievement.
-Once you are Level 7 choose to be Jason Part 7 and load up any map (This is a Grab Kill so you do not need a specific setting) ***Easiest to do this in a private match with a friend***
-Find a Counselor and do a neck grab by pressing Left Trigger
-Look at your grab kill options in the bottom right corner you should see a picture of a machete through a head.
***NOTE if for any reason you dont see the grab kill go into customize for JASON PART 7 and look for Weapon grab kills you can purchase the Dismember Kill (Middle choice of the 3 that are there) for 500CP and equip it***