Allah has prepared for them a severe punishment. Indeed, it was evil that they were doing.
The Saheeh International Quran Translation
أَعَدَّ ٱللَّهُ لَهُمْ عَذَابًا شَدِيدًا إِنَّهُمْ سَآءَ مَا كَانُوا۟ يَعْمَلُونَAllah has prepared for them a severe punishment. Indeed, it was evil that they were doing.