Don't forget Obama also drone striked an American citizen, Anwar al-Awlaki. Fairly confident to say that targeting and killing an American citizen is the prime example of extra-judicial killing.
Sure, some people will be happy that an alleged terrorist was killed. However the legal justification by David J. Barron (Chief Legal Counsel) laid out the the groundwork for a future targeted extra-judicial killing of an American citizen.
You know who's currently in the US crosshairs? Trans people, leftists, immigrants, and anyone who's a non-White, cis, conservative, male.