This idea is so important that Allah (or his prophet) repeats more than 200 times in the Quran. Here are just a few variants.
For disbelievers is a painful doom. 2:104
Those who disbelieve the revelations of Allah ... promise them a painful doom. 3:21
Give tidings (O Muhammad) of a painful doom to those who disbelieve. 9:3
Those who vex the messenger of Allah, for them there is a painful doom. 9:61
Theirs will be a boiling drink and painful doom because they disbelieved. 10:4
And that's just a sample of the 60 verses in the Quran that describe the "painful doom" that unbelevers will endure. There are also 25 "awful doom" verses, 10 "shameful dooms", 4 "dreadful dooms", 4 "dooms of fire", and another 40 or so differently named dooms. Plus 65 verses that mention just a plain old "doom" -- and a couple hundred or so that describe Hell, the Fire, etc.
But my favorite doom verse is this one (If you don't believe in hell, guess where you'll be going):
Those who believe not in the Hereafter, for them We have prepared a painful doom. 17:10