Marguerite de Valois, François Clouet, 1572.
The Malcontent is a character type often used in early modern drama. The character is discontent with the social structure and other characters in the play. He or she is often an outsider, who observes and offers commentary on the action and may even show awareness that they are in a play. Shakespeare's Richard III and Iago in Othello are typical malcontents.
The role is usually both political and dramatic; with the malcontent voicing dissatisfaction with the usually 'Machiavellian' political atmosphere and often using asides to build up a kind of self-consciousness and awareness of the text itself which other characters in the play will lack to the same extent.
Important malcontents include Bosola in Webster's The Duchess of Malfi, the Duchess of Malfi is a macabre, tragic play, written by the English dramatist John Webster and first performed in 1614 at the Globe Theatre in London. The Duchess was Giovanna d'Aragona, whose father, Arrigo d'Aragona, Marquis of Gerace, was an illegitimate son of Ferdinand I of Naples. Her husbands were Alfonso Piccolomini, Duke of Amalfi, and (as in the play) Antonio Bologna. the play begins as a love story, with a Duchess who marries beneath her class, and ends as a nightmarish tragedy as her two brothers exact their revenge, destroying themselves in the process, the play is sometimes ridiculed by modern critics for the excessive violence and horror in its later scenes. Nevertheless, the complexity of some of its characters, particularly Bosola and the Duchess, and Webster's poetic language, give it a continuing interest, and it is still performed in the 21st century.
Malevole in Marston's The Malcontent.
Iago in Shakespeare's Othello, the character's source is traced to Giovanni Battista Giraldi Cinthio's tale "Un Capitano Moro" in Gli Hecatommithi (1565). There, the character is simply "the ensign". Iago is a soldier and Othello's ancient (ensign or standard bearer). He is the husband of Emilia, Desdemona's attendant.
Hamlet in Shakespeare's Hamlet.
The morality and sympathy of the malcontent is a massive variable, as we can see in the examples listed above. Sometimes, as in Hamlet and The Malcontent, they are the sympathetic centre of the play, whereas Iago is a very unsympathetic character.
The most important thing about the malcontent, is that he is malcontent—unhappy, unsettled, displeased with the world as he sees it—not at ease with the world of the play in which he finds himself, eager to change it somehow, or to dispute with it. He is an objective or quasi-objective voice that comments on the concerns of the play and comments as though he is somehow above or beyond them.
The concept has a lot to do with the Renaissance idea of 'humours' and a surfeit of 'black bile' which caused melancholy.
La tentación de San Antonio, Salvador Domingo Felipe Jacinto Dalí i Domènech, 1949. 
