I found a repeatable location with enemies to get these three achievements:
Squash and Run
In John’s region / Holland Valley, towards the top left of his region (middle left of the overall map), there is person that will give a story mission named Merle Briggs. He is located at the fast travel location called Silver Lake Trailer Park
He is being held captive with 4 guards, close to a vehicle, all within a close vicinity of each other.
Because he needs to be freed, you can attempt anything you need and then fast travel back to the location with the enemies reset.
I find this MUCH easier than attacking an outpost
You can sabotage the truck (you might have to have the enemy come closer to it) without being seen.
If you fail, you can just fast travel back to the same location and try again
I recommend highlighting the enemies with your binoculars first - it never seemed to work for me when I didn't.
You can only get 1-4 per try, but distract one enemy at the starting point (from fast traveling) and then the enemy on the far left. After those two, you can try to distract the other 2 "middle" enemies.
I does not seem to count the same enemy twice, so after a max of 4 enemies distracted, if you fail, or if nothing registers, you can just fast travel back to the same location and try again.
Squash and run:
Grab a vehicle and drive up to the location, or grab the truck and run over the 4 enemies.
Once they are all dead, or if you fail, you can just fast travel back to the same location and try again