User blog comment:EmpyreanSmoke/Supernatural Q&A (Closed)/@comment-172.101.67.105-20151114151020/@comment-24834479-20151114215342

1. Lucifer

2. I wouldn't think he could smite beings that high, but with the mark its still open as a possibility.

3. It is unknown what beings the colt cannot kill.

4. All archangels might be immune.

5. That enabled him to awaken from his coma, not keep him alive.