Why did he
kill Qyburn?
Was that just for stepping beside him and commanding him to listen to Cersei? It felt out of character for such an obedient beast.
From what i know, Gregor and Sandor really have a hatred to each other, it may be that Gregor had such a blind hatred towards his younger brother that he wouldn't let anything stand in his way. Not even his obedience towards Cersei and Qyburn