Rhodesia deserves mention given the white minority rule, their pariah status (they certainly were an occupying power, and not a very nice one), and how long they managed to hold on. The Selous Scouts especially were impressive at their job, since just their unit killed several times as many guerillas as the rest of the Rhodesian military. Just look at Operation Eland. There's also Operation Dingo, where about 200 Rhodesians allegedly killed 3000 guerillas and wounded another 5000.
The trick seems to be using deception and infiltration of the enemy force to set up what are basically massacres since most of the guerillas killed in operations like these were unarmed at the time of their deaths.