What is the most brutal trap/torture from Saw?

I know girl got away, but it was some kinda device on her head connected to her jaw and she had to unlock a device- otherwise it will set of and basically rip her head off from jaw. It was horrible. I watched every movie- every scene and I could watch but this one was very hard. I'm very sensitive to pain related to mouth, jaw, teeth. I couldn't stop myself thinking how would it feel if it actually went off. It simply creeps me out..