But We will surely cause those who disbelieve to taste a severe (41:27)

﴿فَلَنُذِيقَنَّ الَّذِينَ كَفَرُوا عَذَابًا شَدِيدًا وَلَنَجْزِيَنَّهُمْ أَسْوَأَ الَّذِي كَانُوا يَعْمَلُونَ﴾
[ فصلت: 27]

41:27 But We will surely cause those who disbelieve to taste a severe punishment, and We will surely recompense them for the worst of what they had been doing.

So we will definitely make those who disbelieved in Allah and rejected His messengers suffer from a severe punishment on the Day of Judgement.
I will definitely requite them with a punishment for the worst of their actions, i.
e.
ascribing partners with Allah and sins.

But surely, We shall cause those who disbelieve to taste a severe torment, and certainly, We shall requite them the worst of what they used to do.

phonetic Transliteration

Falanutheeqanna allatheena kafaroo AAathaban shadeedan walanajziyannahum aswaa allathee kanoo yaAAmaloona

Abdullah Yusuf Ali - Translation

But We will certainly give the Unbelievers a taste of a severe Penalty, and We will requite them for the worst of their deeds.

Safi-ur-Rahman al-Mubarakpuri

But surely, We shall cause those who disbelieve to taste a severe torment, and certainly, We shall requite them the worst of what they used to do.

Page 479 English transliteration