How do I defeat an enemy with every resistance?

Orthog Pain-Lover has been giving me a lot of trouble. He and his goons of spear-throwing hunters killed me a couple times, and it seems he's managed to get every resistance. I can't damage him with:

• Melee attacks
• Ranged attacks
• Steal Attacks
• Draining

He's not immune to monsters, but I've seen him 1-hit caragors (that's part of how he got so powerful; multiple Beast Hunt events), so I don't feel great about that approach.

How do I kill Orthog?

Solution 1:

If an enemy is feared, their strengths will be lessened or negated.

In the case of Orthog, blowing up two nearby campfires when a feast event came up panicked him, and I could damage him with melee attacks in that state.

Pictures for those who want to relish in victory: