How many different ways can you pronounce ough?

What sequence of letters has the most different pronunciations?

That prize goes to -ough. Say these words: bough, rough, through, cough, dough. You will see that not one of these words sounds like any of the others. These are all native Anglo-Saxon words, not products of foreign borrowings. There are seven different ways to pronounce -ough: 1) though (like o in go), 2) through (like oo in too), 3) cough (like off in offer), 4) rough (like uff in suffer), 5) plough (like ow in flower), 6) ought (like aw in saw), and 7) borough (like a in above). Fortunately -ough is an extreme example and English words are not always that difficult to pronounce. In general, when you learn a new word, you should also make sure you know its pronunciation. Look in a dictionary and learn the pronunciation symbols. After that, you will always be able to find the pronunciation of any word. Try it with the seven -ough words above.
There may be one extra way at least - 8) hiccough (like up in cup)