1.moody and suspicious- at the beginning of the play, he appears to be a tyrant:greedy for fame and power. he is moody and suspicious. in act 1, le beau, a courtier, warns orlando of the duke's moody nature, advising him to flee from the duke's dominions.
duke frederick's treatment of rosalind is equally tyrannical. having practically requested rosalind to stay at the court after her father's banishment and to give company to celia- he suddenly orders her to leave the dukedom. his reason for banishing her is that she is the daughter of a traitor. he doesn't listen to celia, own daughter, when she pleads for rosalind. he tries to prejudice celia against her cousin.
he banishes rosalind even though all the evidence shows that she had given him all possible respect. his own daughter calls him a man of harsh and envious mind. duke frederick appears to be suspicious. he always reagarded all honourable men with hostile suspicion including sir rowland de boys and orlando.
2. envious- duke frederick wants fame and is envious of the popularity of others. he considers people as obstacles in the way of his winning the affection of his subjects. envy was his real reason for banishing rosalind.
3. vindictive- duke frederick is shocked to learn that celia has run away with rosalind. he thinks that some of his own courtiers have conspired and aided the flight of the two ladies. on being told that orlando had won the favour of the ladies, and might hace accompanied them, duke frederick offers his officials to look for him and to bring his brother oliver ti him in case oralndo cannot be traced. later, when the officials bring oliver to the court, duke frederick deals sternly with him. he feels that oliver might have been involved in orlando's excape. he therfore orders oliver to bring his brother to the court.
oliver's lands and property are to be seized by the duke's officials and are to be restored to him only when he produces orlando before the duke. when oliver says that he had never in his life loved his brother, orlando. duke frederick replies that if such is the case, oliver is more of a villain than he had first appeared to be. he then orders the officials to push oliver out of his court and to take his entire estate in his custody.
4. his humanity- duke frederick is a tyrant who rules by fear- the principle underlying all despotism. however, the cruelty of his actions is mitigated in a few cases. in the beginning he dissuades orlando from fighting with the proffesional wrestler, and minimises the risk to orlando by permitting him "but one fall". he treats oliver with leniency by giving him time of one year to find orlando.
5. his sudden conversion- towards the close of the play, duke frederick, who had actually come to the forest of arden with a large force to slay his brother, comes across a hermit who transforms him entirely. he decides to renounce the worldly life and to spend the rest of his life in the forest as a hermit. duke frederick's sudden conversion hints at the existence of some nobility within him which had been hitherto suppressed by his ambition,greed and love for popularity.