Assassin

[thejeff]

Assassins are good when used in bulk. Sure, one assassination and they patrol and catch him, having lost one commander. So do a dozen assassinations on that first turn.

Or target blood hunt provinces (unless he's patrolling for unrest) or forts without large armies in them.
Or better still armies about to attack. You kill a couple of commanders, all their troops stay behind. They attack at half strength and get wiped out.