1. John was said to be filled with the Holy Spirit from birth (or from his mother's womb). He was influenced by the Spirit his entire life! No sinful baggage to deter him. He was single-minded and devoted. This would make him as close to being like Christ as would be possible at that time. I don't think this was said of any other mortal.
2. As Joseph M. pointed out, he was, nevertheless, mortal. One in the Kingdom would be immortal.
3. John was a transition from old to new. He preached a "baptism of repentence for the forgiveness of sins." He didn't send people to the Temple to make sacrifices. He bypassed the priests.
4. My personal thinking about John's role is that God impressed people to come to John for baptism. It was a calling to all who would listen. The people that responded were those who humbled themselves. The religious leaders did not come to John. Thus, the separation had begun. Those who came to John had the humility to accept Jesus as the Chosen One, the Son of David. Humility was necessary for righteousness. So why did Jesus come to John for baptism? He had no sins to confess, but he did so in response to the general call of the Father and leading of the Spirit.
5. I've always understood the word "violent" as being too strong, like the way "hate" is used. Could we substitute "assertive" for "violent"? Entering the Kingdom requires an act of will, a choice and action. It's like a prize you have to fight for.