Do you think that is really going to stop me? An Angel of the Lord?
~ Tamiel's arrogance which gets himself killed

Tamiel was an antagonist in Supernatural season ten and he was a very powerful angel, far more powerful than a Seraph even. Castiel was a Seraph at the time yet he had difficulty fighting Tamiel.

Tamiel had existed for millennia and was in charge of watching early humans after Eden. Tamiel was of the Grigori, one of the most powerful and high-ranking angels. He was very skilled at fighting and very arrogant.

He fed on human souls. The Grigori had gone from protectors of humanity to wreakers of havoc, and they found humans ridiculous and lower than them. Tamiel was no exception, he took delight in sadistically taunting his victims.

Amelia Novak had been lured to him, because she was emotionally damaged after her husband Jimmy became Castiel's vessel and left her, and she went to what she believed was a faith healer for healing. However, the exact opposite happened, and Tamiel trapped her and fed off her by cutting her body open round her shoulders and other parts. This was so he could feed on her soul.

Claire Novak, Jimmy and Amelia's daughter, was tracking her mother. She met Castiel, possessing her dead father, and he helped her find Amelia, and she found Amelia almost weakened to death. Tamiel attacked both of them, threw Castiel across the room when he tried to intervene, and when Claire shot Tamiel several times, Tamiel just sneered. Then he beat up Claire and was about to kill her, yet Amelia rushed in front of his sword, impaling herself and dying. (However she was reunited with her husband in Heaven.)

Tamiel tried to stab Castiel but to his shock Claire stabbed him from behind, ending his killing spree.