When the Duke of Brachiano gets killed in the last act of the play, Flamineo—his former ally—pays tribute to him, after Francisco (in disguise) asks him about the Duke:
Flam. He was a kind of statesman, that would sooner have reckoned how many cannon-bullets he had discharged against a town, to count his expense that way, than think how many of his valiant and deserving subjects he lost before it.
Fran. Oh, speak well of the duke!
Flam. I have done. (5.3)
The Duke would probably be proud of this unflattering tribute: Brachiano's just a rotten guy—he betrays and murders his own wife, and kills Vittoria's husband as well. But, weirdly enough, he seems to quite genuinely love Vittoria—calling out for her on his deathbed (5.3). Who says that evil people can't have a sprinkling of humanity?
Originally, Brachiano was married to Isabella (sister of Francisco de Medici)—but that marriage didn't work out so well. He successfully betrays his own wife by seducing Vittoria, and ends up murdering his poor wife, Isabella. Despite the fact that Brachiano is such a villain, his son, Giovanni, is one of the few good characters in the play—though he's pretty young, so there's always time to get corrupted. (We're probably meant to assume he takes after his mother.)
Although Brachiano loves Vittoria, he's also a cad in terms of the way he excuses his own actions. When he intercepts the fake love-letter Francisco sends to Vittoria, he blames Vittoria's beauty for leading him astray—as though that was the real cause of Camillo and Isabella's murders. Brachiano takes this all back in a moment or two, and he and Vittoria elope, but it's still a good example of his psychology, his attitude towards his own actions, and the casual misogyny shared by a lot of the male characters in this play:
Right! there are plots.
Your beauty! Oh, ten thousand curses on 't!
How long have I beheld the devil in crystal!
Thou hast led me, like an heathen sacrifice,
With music, and with fatal yokes of flowers,
To my eternal ruin. Woman to man
Is either a god, or a wolf. (4.2)
Finally, when Brachiano gets his comeuppance, the poison Lodovico and Gasparo put on his helmet ends up frying his brain. In the moments of insanity, before Lodovico finally strangles him, the Duke sees the devil—with a "cod-piece…stuck full of pins." This must be the play's verdict on Brachiano's own uncontrollable passions—his adulterous desires are represented by this weird image of a pin-riddled cod-piece (which is basically a loincloth).