Jack makes a face because he's pretty sure he can kill it, he's powerful, he's just not in control all of it yet. His father or Michael probably could, but he's not them. It's a point of frustration for him that the only people who could truly train him are their worst enemies. But that's not a problem for right in this moment. Getting free with Castiel has to take priority from proving he's stronger than this creature. That would be a Lucifer priority.

I have an idea. Put your hands over your ears and get ready to run past it. If it has no eyesight to get blinded, it means it must rely on hearing. Them moving will only gain its attention, although they both can be quiet if they need to. Jack's not good at that yet either. He whistles on purpose to get the creature's attention, unafraid despite all the reasons he should be, because it means Castiel can move around.

The plan is obvious because once he sees Castiel's hands on his ears, Jack screams. Not the way people do, but the way angels do. The first thing he did when he was born was scream so loudly at Sam and Dean it threw them across a room. It wasn't the last time. Sonic power radiates out of him as it fills the air with high-pitched noise. The creature not only is blown back but it shrieks in pain as it clutches its head, that attack hurting more than any of his others combined.

Jack keeps screaming at it as he moves forward and past it, aiming his voice away from Castiel but trying to put space between them and the creature. He's not sure if he could do this until it died but the space around it starts to shake too from the sheer blast of it. The waves of power crumbles the area but it stands for now.