The Queen's got high hopes for her son Cloten: she wants him to marry Imogen and inherit Cymbeline's crown. But when that doesn't work out, she figures she'll just kill off Imogen and give her son the keys to the kingdom for him to use all by himself. Sounds like a plan, right?
Too bad Cloten's an absolute idiot. He brags about himself wherever he goes, but everyone can see he's a fool. While he might be shocked that Imogen chose someone else over him, a random lord tells us, "[I]f it be a sin to make a true election, / she is damned" (1.2.27-28). Oh, snap. Even a no-namer understands that Cloten is just full of himself.
Shakespeare gives us comments again and again from characters about Cloten—all of which support the idea that he's just a spoiled, arrogant brat. We're even told everyone feels sorry for Imogen because Cloten is "more hateful than the foul expulsion is / of thy dear husband" (2.1.60-61).
Yikes. Turns out no one likes spoiled a mamma's boy. Cloten might complain about having "such [bad] luck," but truth is that he's just catered to because he's in the royal family (2.1.1). Everyone knows he's only praised because he's the Queen's son; the trouble is, this dude actually believes all the praise. It almost sounds like this guy's got one of some of those scary Gen Y entitlement problems.
Word to the wise: don't go comparing Cloten to Posthumus to his face anytime soon. When Imogen finally spells it out for Cloten directly, he flips out. He can't believe she calls him worse than Posthumus's old grungy clothes.
He rants at her: "You sin against / obedience, which you owe your father. For / the contract you pretend with that base wretch" (2.3.128-130). You really want to convince Imogen to marry you because her dad said so? Good comeback, Cloten.
But his particular form of revenge is no laughing matter: he proclaims that Posthumus's clothes "within this hour / be off, thy mistress enforced, thy garments cut to / pieces before thy face" (4.1.17-19). While he doesn't actually get a chance to go through with the rape, he fully intends to, which is scary. He doesn't even seem to think there's anything wrong with this: he just wants to get his way, and nothing is going to stop him.
Cloten's cockiness and arrogance eventually get him into a fight he can't finish. It's pathetic, in a way: we're sure it never even crossed Cloten's mind that he could lose the fight against Guiderius. Shakespeare seems to kill off the characters in this play who just can't atone for what they've done, and Cloten, we're sorry to say, seems to be just too self-unaware to survive in a world his evil mother isn't controlling.