Bad word that will curse a family Background

So my friend, who’s Chinese, cried a few weeks ago.

Apparently, a boy(let’s call him Bobby) in our class said a ‘bad word that will curse a family and their generation forever’. I asked what it was but all she said was...


  Do you want me to curse your family? sniff


And then broke down in tears.

If I was her, I would have just ignored it and laughed.

Question

What is the word/phrase that Bobby used? Is it really bad?
If it was Cantonese, it would obviously be 冚家剷 (entire family die)

Since it was Mandarin,  the only common phrases that curse someone's entire family I can think of are:


絕子絕孫 (no male descendants, the family line ends) 
男盜女娼 (one's male descendants will be thieves and female descendants will be prostitutes)


Or it can be any cursing phrase with '你全家' before it. For example "你全家不得好死" (all of your family members will die a horrible death)