Someone in the FAQ thread experienced many opposing armies that were basically defenseless after one combat turn, because they lost all their action points. He confirmed that he picked a sovereign with the "Intimidating" trait, which is proof that it is very effective.
I once created a sovereign with the "Cruel" trait and stopped playing with him because of it. My sovereign and most of the hired champions lost their action points after one turn and were butchered most of the time.
