We really only see (hear from) Prince Escalus of Verona three times in Romeo and Juliet by William Shakespeare, and he only speaks about 500 words in the entire play. He is both a man who shows no mercy and a man of compassion.
In the first scene in which the Prince appears, a fight has broken out in the city--again. The Capulets and the Montagues are in a feud, and the entire city is suffering because they are quick to fight. In this scene, the Prince is acting as a strict disciplinarian; he is not happy with the behavior of these two grown men and his tone is angry and threatening.
Rebellious subjects, enemies to peace,
Profaners of this neighbour-stained steel,--
Will they not hear? What, ho! you men, you beasts,
That quench the fire of your pernicious rage
With purple fountains issuing from your veins,
On pain of torture, from those bloody hands
Throw your mistemper'd weapons to the ground,
And hear the sentence of your moved prince.
He says that this this is the third time the two factions have been involved in "civil brawls" which have wreaked havoc in town, so he makes an edict:
He orders Montague and Capulet to meet with him privately later in the day, and there is no doubt that the Prince is justifiably angry and means business. His word is law, and he delivers it with strength.
We meet the Prince again only when another act of violence erupts on his city's streets. Mercutio, Romeo, and Tybalt have been fighting, and now all three are gone. Mercutio and Tybalt are dead; Romeo has run off at the urging of his friends, as they are fully aware of the Prince's edict against fighting in the streets. He asks what has happened and then pronounces his sentence on Romeo: Romeo is now immediately exiled.
It is interesting to note that the Prince had every right to have Romeo killed, as that is the law he decreed. Instead, he shows limited mercy because he understands why Romeo was moved to kill Tybalt. He knows how Romeo feels, of course, because Mercutio was his kinsman (relative); however, he imposes a strong enough penalty that they will regret their actions toward the Prince's family. He will not be moved by tears, "pleading and excuses"; he has to punish Romeo because he understands that if he shows mercy by pardoning murderers, he will only promote more murders.
At the final act of violence in the play, we see the compassionate aspect of the Prince's character. Everyone is mourning a tragic loss, and though the Prince is still businesslike in his approach to trying to figure out what happened, he also demonstrates true compassion.
Once he has learned about the events which led up to this tragedy, he calls the two fathers to him again, this time he commiserates a bit with them, for all three of them have lost someone they loved to the men's ridiculous feuding. In his last speech, the Prince is clearly in mourning. While he will still do what he must, he is full of sorrow.
A glooming peace this morning with it brings;
The sun, for sorrow, will not show his head:
Go hence, to have more talk of these sad things;
Some shall be pardon'd, and some punished:
For never was a story of more woe
Than this of Juliet and her Romeo.
Clearly the Prince does what he must as the strict and merciless leader of his city; however, he also demonstrates that he is a man of compassion who understands sorrow and loss. These are the two sides of the noble Prince.