﴿ فَلَنُذِيقَنَّ ٱلَّذِينَ كَفَرُوا۟ عَذَابًۭا شَدِيدًۭا وَلَنَجْزِيَنَّهُمْ أَسْوَأَ ٱلَّذِى كَانُوا۟ يَعْمَلُونَ ﴾

“But We shall most certainly give those who are [thus] bent on denying the truth a taste of suffering severe, and We shall most certainly requite them according to the worst of their deeds!”

God exalted be He says regarding them But verily We will make those who disbelieve taste a severe chastisement and We will verily requite them the worst of what they used to do in other words with the worst requital for their deeds.