Thank you for the question on the uniqueness of the Gospel of Mark.
For one’s consideration, here are some thoughts for consideration.
A. Mark is not written by one of the 12 Apostles but probably under the direction of Peter.
B. Mark is the shortest Gospel of the Four Gospel,
C. Mark doesn’t include the birth or childhood of Jesus.
D. Mark has fewer citations of Jesus’ teachings and private conversations.
E. Mark depicts Jesus as the Servant doing the will of God.
F. Mark has an abrupt ending to the resurrection of Jesus.
G. Mark may have been one of the first eyewitnesses written account of the brief life of Jesus.
SUMMARY: The humanity of Jesus is emphasized more than the deity of Jesus. He is the Humble Servant of God.
For further insight and discussion:
https://www.quora.com/What-is-unique-about-the-Gospel-of-Mark