There were two “Reigns of Terror,” if we would but remember it and consider it; the one wrought murder in hot passion, the other in heartless cold blood; the one lasted mere months, the other had lasted a thousand years; the one inflicted death upon ten thousand persons, the other upon a hundred millions; but our shudders are all for the “horrors” of the minor Terror, the momentary Terror, so to speak; whereas, what is the horror of swift death by the axe, compared with lifelong death from hunger, cold, insult, cruelty, and heart-break? What is swift death by lightning compared with death by slow fire at the stake? A city cemetery could contain the coffins filled by that brief Terror which we have all been so diligently taught to shiver at and mourn over; but all France could hardly contain the coffins filled by that older and real Terror—that unspeakably bitter and awful Terror which none of us has been taught to see in its vastness or pity as it deserves.
Cromwell was a monster reacting to a monstrous system. History is quick to pass judgement the former while ignoring - and in the case of England unlike France, perpetuating - the latter.
Which British monarch has their hands dirty with the blood of millions? The obvious cases where British policy led to that many deaths would be e.g. the Irish and Bengal famines (the latter during WWII). Those both took place at a time when the monarch was a constitutional figurehead.
The best case might be the slave trade. But this was at its height under the Hanoverians, by which time the Commons was already the effective supreme power. I suppose you could say that the slave trade started earlier, and that this starting event caused the later expansion. Maybe, but that's a claim about the causal chain that needs arguing for.
Sure, and this is generally regarded as a bad thing.
Cromwell gets defenders for opposing them, despite committing many of the same bad things, and in the case of Ireland, even harsher actions with longer term consequences.
Complaints about the british monarchy don't excuse Cromwell his actions.
You have to remenber that things we take as granted nowdays, may have been divisive at the time.