Cromwell remains a controversial figure due to his use of the army to acquire political power, and the brutality of his 1649 campaign in Ireland. He had men torched taking refuge in a church and slaughtered civilians. He also, instituted the Penal Laws.
The penal laws were, according to Edmund Burke, Anglo-Irish statesman and philosopher "a machine of wise and elaborate contrivance, as well fitted for the oppression, impoverishment and degradation of a people, and the debasement in them of human nature itself, as ever proceeded from the perverted ingenuity of man."
Irish Mythology - Mythical Cycle - Book of Invasions