User blog comment:Gabrielaaloo/Jack Vs Jesse Turner/@comment-31057575-20180507100845/@comment-26982641-20180508102018

And Castiel has never been wrong? He is meant to be Lucifer's weapon against Heaven but we saw that even a demon-killing knife was capable of killing the Cambion. On the other hand Jack is completely invulnerable to angel blades, angel banishing sigil etc.