The Prophet ﷺ said, "Oppression will be a darkness on the Day of Resurrection." (Using translation from Bukhārī 2447)

أَنَّ رَسُولَ اللهِ ﷺ قَالَ الظُّلْمُ ظُلُمَاتٌ يَوْمَ الْقِيَامَةِ