Castiel's personality changed after he absorbed the monster souls from Purgatory and gained god-like abilities to kill the archangel Raphael.

He glared at you, Dean, and Sam as Sam’s attempt to stab him with an angel blade failed. “The angel blade won't work because I'm not an angel anymore. I'm your new god. You will bow down and profess your love unto me, your Lord,” he said sternly.

His gaze was on you as he waited for all of you to kneel before him. He was getting impatient by the minute.