sanctions always benefit the oppressor (read the dictator). While sanctions (in theory) make it harder for a regime to earn money - in practice it leads to more poverty and hardship among the poor people (who don't care about politics). Sanctions usually lead to more anti-foreign sentiments and a boost to the radical power-bases within the sanctioned country. Walking a country (society) back from the effects of sanctions is incredibly tricky and requires more than just undoing the sanction.