You need a pet. Mount with terror bird will be your best bet. If your target is in town there is little they can do to defend themselves. Dismount in town. Criminal actions off. Prepare fulmination. Cast fulm, prep Tunderlash. On charge on Tlash attack with pet. The target will die as soon as you release the Tlash.
What I just explained is one of the many reasons why the bounty hunting system is terrible. The victim has no idea and quite honestly has no way to defend themselves. If they attack you, the mage, they will either hit other players, or you will parry their attacks until the bird kills them. If they attack the bird, you can heal the bird and corrupt the target.