When I meet someone who speaks a foreign language, I always ask him or her about all the four-letter words in that language. After years of 'research', I have reached the conclusion that, when it comes to swearing, the Cantonese have no equals. Like everything else in Cantonese, the swear words are vulgar but apt. Let me give you some examples.
While people from most countries would settle for insulting just you, a Cantonese man insults your mother. In saying that, it is implied that he could be your father, therefore you are a bastard and your father is a tortoise - someone who shares his wife.
Sometimes a Cantonese man can get so carried away with rage that he swears at his children the same way, until a bystander reminds him: 'Hey, that's what you are supposed to do anyway.' With a few choice words, he also describes the sorry status of your mother's reproductive system, so that everyone knows that your mother has an incurable infectious disease. Why anyone would want to boast about having a liaison with a woman like that is beyond me.
Every language has a name for a guy who is no good. Depending on the situation, the English language labels him a jerk, a nerd, a nincompoop, and you know the rest and the best. The Cantonese call him that too, except that he is also in an aroused state. That makes sense, because if most of that guy's circulation is drawn to that part of his anatomy, the brain is sure to be deprived of oxygen, hence his behaviour and demeanour.
Those same words are used to describe someone who is ugly. Come to think of it, nothing can be uglier than having a face which resembles a sexual organ in an aroused state.
Sometimes a whole family is cursed. A curse of that magnitude calls for some tact, even for the Cantonese. So you hear something like: 'Your whole family will get rich.' Do not thank him yet. What he meant was you and every member of your clan would be offered the kind of money which comes in million dollar denominations and is burned in bundles at funeral homes.