[Satan] Beautified for them their works.

زَيَّنَلَهُمُالشَّيْطَانُ أَعْمَالَهُمْ

Zayyanalahum ash-shaytana a’maalahum
[Satan] Beautified for them theirworks.
[Anfal 8:48]

‘Aml عملinthe Qur’an usually implies good deeds/works.
Soo’u a’maalahum (سووعأعمالهم ) is for their evil deeds.
So shaytan is beautifying for the disbelievers their good deeds. This is what it seems like from the words used.
People do alot of evil deeds, then they might do a small good deed. Shaytan makes them remember the small good they might have done but they forget the huge evils they have also done. So shaytan beautifies this small good, and the person thinks they are really pious, and that this good deed is sufficient for them to be saved from Allah’s punishment.
A beautiful example of this is in surah Shu’ara 26:18-22. Where Pharaoah reminds Moses the favour of his upbringing of Moses when he was a child.


قَالَأَلَمْنُرَبِّكَفِينَاوَلِيدًاوَلَبِثْتَفِينَامِنْعُمُرِكَسِنِينَ.وَفَعَلْتَفَعْلَتَكَالَّتِيفَعَلْتَوَأَنتَمِنَالْكَافِرِينَ.قَالَفَعَلْتُهَاإِذًاوَأَنَامِنَالضَّالِّينَ.فَفَرَرْتُمِنكُمْلَمَّاخِفْتُكُمْفَوَهَبَلِيرَبِّيحُكْمًاوَجَعَلَنِيمِنَالْمُرْسَلِينَ.

[Fir’aun (Pharaoh)] said [to Musa (Moses)]: “Did we not bring you up among us as a child? And you did dwell many years of your life with us.
“And you did your deed, which you did (i.e. the crime of killing a man). And you are one of the ungrateful.”
Musa (Moses) said: “I did it then, when I was an ignorant (as regards my Lord and His Message).
So I fled from you when I feared you. Then my Lord granted me wisdom and prophethood and appointed me [as one] of the messengers.
[Shu’ara 26: 18-21]
Then Moses reminds him that he accepts that favour, but does that justify the enslavement and abuse of all the Banu Isra’eel people?

وَتِلْكَنِعْمَةٌتَمُنُّهَاعَلَيَّأَنْعَبَّدتَّبَنِيإِسْرَائِيلَ

“And this is the past favour with which you reproach me, that you have enslaved the Children of Israel?” [Shu’ara 26:22]
How can you compare these 2? Your evil is much worse than the little good you have done.
Shaytan had beautified his small good, making him forget his evil.