Who is Tybalt? What makes him a villain?

In
Shakespeare's ,is a member of the Capulet clan, a cousin to , and the
nephew of . Although, without question, he's a hot-blooded and even bellicose young man, he
hardly could be called a villain. He's surely as much a victim of the bloody conflict between
the warring families as the eponymous lovers.

In ,becomes infatuated with
Juliet after sneaking into a ball at the home of her family. Tybalt, greatly angered by the
stealthy entry of his family's enemy, is on the verge of drawing his sword when he's stopped by
Juliet's father, Capulet, who forbids violence in his home.

When they next
meet on the street in , Tybalt, still enraged by Romeo's transgression, challenges him to a
duel, unaware that he's now married to his young cousin. For this reason, Romeo refuses the
challenge, which angers his friend, who accepts in his place. When Romeo steps in to stop the
fight, Mercutio is accidentally killed. Now...