54:21

فَكَيْفَ كَانَ عَذَابِي وَنُذُرِ

Transliteration:

Fakayfa kana AAathabee wanuthuri

Word by Word:

So how was My punishment and My warnings?

Translations:

for, how severe is the suffering which I inflict when My warnings are disregarded!

Yea, how (terrible) was My Penalty and My Warning!

Then see how (dreadful) was My punishment after My warnings!

And certainly We have made the Qur'an easy to remember, but is there any one who will mind?

And how [severe] were My punishment and warning.