عن إبن عمر رضي الله تعالي عنهما أن النبي صلي الله عليه وسلم قال: الظلم ظلمات يوم القيامة
Ibn Amr رضي الله تعالي عنهما narrates that our prophet صلي الله عليه وسلم said: Injustice will come in the form of darkness on the Day of Judgment. [Bukhari]

'Injustice will be in darkness on the day of judgment'
The light (noor) that a believer will have on that day, a person who did injustice in the world he will not have that noor with them.

A few ulamas have said that the word 'darkness' used in this hadith means troubles and hardships. So that person who did injustice will go through many troubles on that day, as to which Allah has said

قل من ينجيكم من ظلمات البر ولبحر
say who can free you from the river of hardship and trouble.

Islam encourages brotherhood between everyone but with injustice this is not possible

Allah has said in one hadith-e-qudsi

يا عبادي اني حرمت الظلم على نفسي و جعلته بينكم محرما فلا تظالموا
'oh my servants i have made injustice haraam on me and i have also made it haraam between you. So do not be unjust with each other.'