Are there any letter combinations that have as many different sounds as -ough in English?

As far as I know, the -ough grouping has the biggest pronunciation variation of any group in English.

  • /ʌf/ enough, hough, rough, slough, tough (rhymes with stuff)
  • /ɒf~ɔːf/ cough, trough (rhymes with off)
  • /trɔːθ/ trough (by some speakers of American English rhymes with cloth)
  • /aʊ/ bough, drought, plough (rhymes with cow)
  • /oʊ/ dough, furlough, though (rhymes with toe and know)
  • /ɔː/ bought, brought, ought, sought, thought, wrought (regularly used before /t/, except in drought /draʊt/. rhymes with taught and “sort” in some accents)
  • /uː/ brougham, slough, through (rhymes with true)
  • /ə/ borough, thorough (in BrE rhymes with bra though both words may be pronounced /oʊ/ in American English accents as in ‘toe’)
  • /ʌp/ hiccough (a BrE variant spelling of “hiccup,” though the latter form is recommended in both British and US. Rhymes with cup)
  • /ɒk/ hough (more commonly spelled “hock” from the 20th century onwards and rhymes with stock)
  • /ɒx/ lough (Meaning a lake in Irish English and an analogue of Scots “loch”, it rhymes with loch)

The second closest, but a long way short, is the -omb group:

  • bomb /bɒm/ (rhymes with Tom)
  • comb /koʊm/ (rhymes with home)
  • sombre /ˈsɒmbə/
  • tomb /tuːm/ (rhymes with gloom).

I can’t comment authoritatively on the spellings within all other languages, but the languages I have learned, all tend to have more logical spelling rules than English. The negative side of this simple spelling is that many languages have large numbers of homonyms, making reading harder.