In the movie Ronan gets out of a tub, gets his hammer, and kills a Nova Corp member. Was he special in any way? I always thought that had to have some significance besides him killing a random soldier.
Currently we have no answer as to the identity of the Xandarian prisoner. Although this can always be retconned in a later film, he is most likely just some random corpsman captured by Ronan's men. Even without knowing the man's identity, however, the scene still serves to show the audience not only Ronan's motivation, but also his villainy & willingness to kill.
Ronan: They call me a terrorist... a radical... a zealot. Because I obey the ancient laws of my people the Kree and punish those who do not. Because I do not forgive your people for taking the life of my father, and his father, and his father before him. A thousand years of war between us will NOT be forgotten.
Prisoner: [struggles in harness] You can’t do this. Our governments signed a peace treaty!
Ronan: Yes, my government knows no shame. You Xandarians and your culture are a disease.
Prisoner: You will never rule Xandar.
Ronan: No... I will cure it! [yells as he swings axe and crushes prisoner's head]
It seems like Ronan is sacrificing the Xandarian. The blood that runs from the prisoner looks a lot like the liquid Ronan appear out of during the opening of the scene.