Just a while ago, I was playing as Juhziz in Challange mode (Hard) against Dr. Thrax who managed to demolish my WHOLE base and all my units save a Palace loaded with RPGs, and four Quad Cannons, and a Jarmen Kell.
Using Jarmen Kell alone, I managed to defeat him. Only problem it was VERY long (you have to demo charge a building 2-3 times to blow the hole as well as the structure). All I had to do is sniper infantry and vehicle pilots, and blow up any structures. His explosives make him a force in his own right.