A revenge tragedy, made popular in Elizabethan and Jacobean Britain, typically tells the story of a protagonist seeking revenge against the murderous actions of an antagonist. Shakespeare's Hamlet is probably seen as the most typical revenge tragedy of those times and the play that popularized many of the genre's conventions, including soliloquies, madness, action-packed scenes, bloody murders, important noble figures, suicide, and the use of disguise.

The Duchess of Malfi is also seen as a revenge tragedy, just not a typical one.

It is a revenge tragedy because, firstly, it features a character, Bosola, who seeks revenge for the murders of the play's most noble characters. Secondly, it features some of the genre's most typical characteristics: soliloquies, sensational murders, madness, and Machiavellian characters.

Soliloquies

Bosola is the only character in the play who gives the audience insight into his true state of mind by speaking his thoughts aloud. For example, at the end of act 4, he shows guilt for arranging to kill the Duchess of Malfi by telling the audience,

All our good deeds and bad, a perspective
That shows us hell! That we cannot be suffer'd
To do good when we have a mind to it!
This is manly sorrow

Sensational murders

Perhaps the most sensational murder of many is when Bosola orders the executioner to kill the Duchess and her children at the end of act 4. Just before the executioner strangles her, the Duchess says,

What would it pleasure me to have my throat cut
With diamonds? or to be smothered
With cassia or to be shot to death with pearls?
I know death hath ten thousand several doors
For men to take their exits. . . .

Dispose my breath how please you.

With the Duchess dead, Bosola tells his men,

some other strangle the children.

Madness

Like Hamlet loses his mind after the death of his father, the Duchess's brother Ferdinand loses his mind in act 5, scene 2 after the death of his sister. At one point he attempts to throttle his own shadow.

Eagles commonly fly alone: they are crows, daws
and starlings that flock together. Look, what's that follows me?
I will throttle it.

Machiavellian characters

The Cardinal is probably the play's Machiavellian character and, though professing to be a man of God, kills his lover by tricking her into kissing the cover of a poisoned bible:

Now you shall never utter it; thy curiosity
Hath undone thee; thou 'rt poison'd with that book
Because I knew thou couldst not keep my counsel
I have bound thee to 't by death

Where The Duchess of Malfi is different from most revenge tragedies is that the protagonist revenging the deaths of the principle characters, Bosola, is the one that either killed them or played a hand in their deaths. Not only that, but he doesn't decide to take revenge until the end of act 5, scene 4, when he says,

I have this cardinal in the forge already;
Now I'll bring him to th' hammer O direful misprison.

Up to that point, the play could just as easily have been a tragedy in the vein of Romeo and Juliet.

It is indeed appropriate to describe The Duchess of Malfi as a revenge tragedy, albeit one that departs in some respects from the traditional definition. Nonetheless, most of the key elements are present. Let's now look at some of them in greater detail:

• Horrors. There are numerous horrors in the play. One thinks of the scene where the Duchess kisses a dead man's severed hand, believing it to belong to the Duke. The grotesque spectacle of the wax figures of the dead bodies of Antonio and the children being presented to the Duchess is yet another particularly creepy example.

• Madness. The Duke deliberately attempts to drive the Duchess mad, yet he is the one who ends up going insane. The theme of madness also feeds into the different angle on revenge presented by Webster, which departs from the traditional conventions of revenge tragedy. In The Duchess of Malfi it's the villains, not the heroes, who seek revenge. The Duchess's wicked brothers are effectively driven mad by their desire to get even; in that sense, they are the victims of their own revenge.

• Characters of noble birth. According to the prevailing dramatic conventions, only the suffering of characters of noble birth were a fit source for revenge tragedy (or any kind of tragedy, for that matter). The nobility had more to lose and further to fall. Indeed, being brought low was in itself thought to be tragic for someone of noble birth such as the Duchess. Tragedy implies some kind of fall, and that's precisely what happens, not just to the Duchess, but also to her evil brothers, who are morally corrupted by their insane, all-consuming desire for revenge.

First, we should think about the definition of a "revenge tragedy." The term was first used by the American Shakespeare scholar Ashley H. Thorndike (1871–1933) in a 1902 article "The Relations of Hamlet to Contemporary Revenge Plays." It has since become a common term in literary criticism used to elucidate the common characteristics of many Elizabethan and Jacobean dramas. The characteristics include

• a plot involving some form of revenge, usually for a past injustice
• a convoluted and action-packed plot structure
• madness
• disguise or other forms of pretense
• violent murders
• many characters dying in the fifth act
• extremely evil villains
• cannibalism
• highly wrought figurative language
• exotic setting (Italy, Spain, etc.)

The play is set in Italy. Ferdinand, the duke of Calabria, is a typical revenge tragedy villain. The plot is extremely convoluted and includes the ruse to send Antonio away and keep the children safe. Many of the characters are murdered near the end of the play.

Although The Duchess of Malfi does not have the classic plot arc of a single avenger seeking and obtaining justice for a past injustice, it has many of the other characteristics of revenge drama and, as a result, most critics consider it a revenge tragedy. 

How is Webster's The Duchess of Malfi a revenge tragedy?

Revenge tragedies were a popular theatrical genre in sixteenth- and seventeenth-century England. These plays focus on a character who experiences a great wrong, such as the murder of a family member or lover, and their subsequent quest to avenge this wrong on the perpetrators. Hamlet is perhaps the most famous revenge tragedy, though ironically, it is one of the most atypical as well, with its philosophical bent. The Duchess of Malfi is similarly atypical due to the central character and the avenger not being the same character within the story.

The titular duchess is the main character of The Duchess of Malfi. Her actions (marrying against her brother's wishes, raising a family while trying to retain political power, etc.) move the plot and cause other characters to react in response. She is ultimately imprisoned, tortured, and murdered by her two wicked brothers. She is even led to believe that her beloved husband and children are all dead before being killed herself. However, the duchess never seeks vengeance for the wrongs done to her. She never even gets the chance.

The spy Bosola is the character who makes this play a proper revenge tragedy. He ends up feeling sympathy for the duchess and after playing a role in her murder, and he decides to avenge her. The resultant revenge is quite violent and even darkly comedic at times.

The play also features several characteristics common to the genre: madness (Duke Ferdinand, already half-mad when the play begins, goes insane after the duchess dies), sensationalist violence, a foreign setting (Italy), and a sense of perverse sexuality (Duke Ferdinand is implied to have incestuous desires towards the duchess and the cardinal has a mistress despite his religious vocation).

Can The Duchess of Malfi by John Webster be called a revenge tragedy?

The Duchess of Malfi contains elements of the revenge drama, a popular form in 17th century because audiences enjoyed the onstage violence and bloodshed. However, it also veers from the classical revenge drama. In a purer revenge drama, such as Hamlet, a hero takes revenge on someone who deserves punishment in order to restore justice and honor to a corrupted environment, but in this play, the brothers act violently against the Duchess not because she has overtly dishonored them, but because they don't like that she has remarried. Their revenge is thus not legitimate. Further, the Duchess, even though the play's heroine and title character, dies before getting revenge on those who hurt her. However, the play does include many dead bodies, a salient aspect of this genre, and Bosola, in a change of heart after participating in their murders, decides he wants to avenge the Duchess and Antonio. Moral corruption, a mainstay of the revenge drama, saturates this play. For example, the Cardinal, who should be an exemplar of Christian chastity and virtue, not only has a mistress, but also murders her.

Can The Duchess of Malfi by John Webster be called a revenge tragedy?

The revenge tragedy is a genre that was common in Elizabethan and Jacobean England. It was modelled primarily on Seneca's tragedies, especially the Medea. The earliest work of the genre is usually held to be Kyd's Spanish Tragedy, but there are many other examples, including The Revenger's Tragedy, Webster's The White Devil (1612) and The Duchess of Malfi (1614),  and Ford's 'Tis Pity She's a Whore, and, of course Hamlet.

These tragedies are normally centered on a protagonist who has been wronged and is seeking revenge in an obsessive manner. They usually feature intense melodrama and violence, moral corruption, and a sort of blank verse with many metrical variations.  They are often set in Italy.