...would be The Crowning With Thorns.
I was taught, and hold to be true, that praying the rasary isn't about reciting the Aves and Gloria Patries...it's about maditationg on the mysteries. That is to say, making yourself, in the sanctuary of inner prayer, present at the events as an observer, to feel what it was like to be there.
When I pray this mystery it works perhaps a little too well. I was a soldier. In many ways I still think like a soldier. I can put myself there, with this guy we think is fomenting rebellion and guerrilla warfare. I can see my self joining in, punching, mocking, spitting upon our Lord. I can see myself to the extent that it's devastating, at times.
And I always come away with the sense that I'm still punching Jesus in the face, every time I sin, every time I turn my back on grace in favor of my own desires or opinions. Because that's what we do. Were we not sinners, each of us, then the Passion would not have been necessary. Were we not sinners the sacrifice at Golgotha would not be needed. So I end this mystery with a profound sense of my own betrayals and disrespect of Christ.
This also why this is also my favorite mystery.