It's just as the title say. Obviously compared to today's moral standards he and admittedly most historical figures were not good. However, there is a lot of controversy around Cromwells massacre of the Irish and those against him have claimed that even for the time this was bad. Although by my understanding, there are arguments supporting him too, claiming that the accusations against his actions as 'ethnic cleansing' to be exagerrations. So essentially what I'm asking is for someone to lay down all the facts.
I've talked a bit before about the questions around Cromwell and conduct in Ireland, especially within the context of the wars happening in Britain, and contemporary continental wars such as the thirty years war. Hopefully this will help a bit until someone else has a more in depth answer.