First, Gannji and Enor are both True Neutral, though Gannji leans a little more Lawful and Enor leans a little more Chaotic.
Second, they were absolutely trying to kill Roy when Enor breathed lightning. A half-dragon's lightning breath does more lethal damage than 99% of the people in the world can withstand. However, remember that in the Empire of Blood, it would have been totally legal to kill Roy on the spot for asking about a legitimate bounty. The only reason it became an issue is because Kilkil "lost" the paperwork.
Third, Enor using it on Elan earlier was representative of the fact that Enor was under the effect of the Suggestion and had no other alternatives to continue attacking. The bounty was "Dead or Alive," and in that moment, Dead seemed doable while Alive didn't (at least to Enor's simple mind). Once the Suggestion was broken, Enor reverted to striking for nonlethal damage.
Fourth, this thread is unnecessarily hostile, and, since I just answered the main question, I'm locking it now.