Constantine: Angels and Ministers of Grace Season 1, Ep 12
John discovers people at a hospital are being murdered because of shards of a prehistorically shattered diamond made of pure evil, to which contact with a human causes insane rage, doubled strength and a desire to kill. Yeah, you read that right.
Constantine: Quid Pro Quo Season 1, Ep 10
John, Zed and Chas race to save Chas's daughter after her soul is taken by an evil wizard.