﴿ لِيُكَفِّرَ ٱللَّهُ عَنْهُمْ أَسْوَأَ ٱلَّذِى عَمِلُوا۟ وَيَجْزِيَهُمْ أَجْرَهُم بِأَحْسَنِ ٱلَّذِى كَانُوا۟ يَعْمَلُونَ ﴾

“And to this end, God will efface from their record the worst that they ever did, and give them their reward in accordance with the best that they were doing [in life].”

so that God may absolve them of the worst of what they did and pay them their reward by the best of what they used to do aswa’a and ahsana mean simply al-sayyi’ ‘bad’ and al-hasan ‘good’.