The Koran spells out stern warnings to nations of disbelievers. The threats and warnings are a reminder that Allah is all-powerful.

L/36:
And how many a generation We destroyed before them, who were mightier than these in prowess so that they overran the lands! Had they any place of refuge (when the judgement came)?

VII/97-99:
Are the people of the townships then secure from the coming of Our wrath upon them as a night-raid while they sleep?

Or are the people of the townships then secure from the coming of Our wrath upon them in the daytime while they play?

Are they then secure from Allah's scheme? None deemeth himself secure from Allah's scheme save folk that perish.

XXII/45:
How many a township have We destroyed while it was sinful, so that it lieth (to this day) in ruins, and (how many) a deserted well and lofty tower!

XXII/48:
And how many a township did I suffer long though it was sinful! Then I grasped it. Unto Me is the return.

VI/6:
See they not how many a generation We destroyed before them, whom We had established in the earth more firmly than We have established you, and We shed on them abundant showers from the sky, and made the rivers flow beneath them. Yet We destroyed them for their sins, and created after them another generation.