General Synonyms:
* Oppressed
* Subjugated
* Exploited
* Abused
* Maltreated
* Harassed
* Persecuted
* Depressed
* Miserable
* Despised
More specific synonyms:
* Humiliated (emphasizes the feeling of shame)
* Defeated (emphasizes the lack of power)
* Broken (emphasizes the psychological impact)
* Disenfranchised (emphasizes the lack of rights)
* Marginalized (emphasizes being pushed to the edges of society)
* Disadvantaged (emphasizes lack of opportunities)
The best synonym to use will depend on the specific context of your writing.