This is pretty much my introduction to custom achievements, always wondered how they worked so I made a mod myself about it.
It's kinda low effort, but to explain how it works :
You need to kill 1000 of each special unit (except marshals for example, since they barely ever spawn) to unlock the dedicated achievement.

Example, if you kill 1000 cloakers you will get the Cloaker Hunter achievement

The graze code (for graze kills to count) and idea comes from Akira's GWM mod (with permission)

You get from 6 to 16 continental coins for each achievement.
(Hunter's Fury idea and logo comes from Tom Clancy's The Division 2's which has a Gear Set of the same name)