Here are some videos on Executive Outcomes and the follow-on Mercs in Seria Leone.
Executive Outcomes defeated 1500 rebels with 150 men in 1995. Here is a video on them. One thing that made a difference was that EO didn't "oppress" the people. Both the Army and the rebels would rape, loot, and pillage the locals, but EO came in and provided aid in exchange for information. They then used that information to destroy the rebels.
https://youtu.be/w34L4Qu2Deg
Here is a follow-up video from 2000
https://youtu.be/I1DCxpnqUzE