the mother of all something

US /ðə ˈmʌðər əv ɔːl ˈsʌmθɪŋ/
UK /ðə ˈmʌðər əv ɔːl ˈsʌmθɪŋ/
"the mother of all something" picture
1.

la mère de tous les, le plus grand, le plus difficile

used to refer to an extreme example of something, often the largest, most impressive, or most difficult one

:
The final exam was the mother of all tests.
L'examen final était la mère de tous les examens.
They faced the mother of all traffic jams on their way to the concert.
Ils ont rencontré la mère de tous les embouteillages en allant au concert.