Among the most salient characteristics of Rasulullah(SAllallahu Alaihi Wasallam) was that he never oppressed anyone, though he was oppressed by many. Instead, he forgave those who oppressed him and never took revenge for his personal self.
Oppressing someone through one's position, influence or wealth is unlawful and unacceptable. Islam teaches us that every human being deserves dignity and respect and to undermine anyone's basic human dignity through oppression is prohibited.
Rasulullah (SAllallahu Alaihi Wasallam) said, “Oppression will be a darkness (for the perpetrator) on the day of Judgment.” (Bukhari)
Rasulullah (SAllallahu Alaihi Wasallam) said, “Help your brother, whether he is an oppressor or he is an oppressed one. People asked, "O Prophet of Allah! It is all right to help him if he is oppressed, but how should we help him if he is an oppressor?" Rasulullah r replied, "By deterring him from oppressing others.” (Bukhari)
Whilst one may get away with oppression in this world, there will be no escaping justice in the Grand Court of Almighty Allah on the Day of Judgement where all deeds will be laid bare.
If we have hurt or oppressed someone through our tongue, attitude or conduct, we need to seek forgiveness from the victim and repent sincerely. Seeking forgiveness requires humility and a resolution never to be an oppressor.