Haig - Agree. Some would argue he was just doing his best, according to the rules of war at the time. But his war of attrition resulted in enormous numbers of British casualties, partly because of his wish to keep his offensives all-British affairs, instead of waiting for support from French and US forces.
Harris - Disagree. I think a WW2 Lancaster crew member summed it up very succinctly:
"If you couldn't get the German in his factory, it was just as easy to knock him off in his bed. And if old Granny Schiklegruber next door got the chop, that's just hard luck."
Cromwell - Disagree - Not quite as bad as Charles I, who claimed to rule by divine right.