It is narrated from Imam Ali (AS) who said:

The oppressors and cruel individuals have three signs;

1.Committing sins against their superiors
2.Oppressing their subordinates by dominating them
3.Supporting oppressors [1].

[1] Mostadrak-o-Nahjul Balaghah, Kashiful Gheta, Page 163.

Source: en.shafaqna.com