This is the time when the Irish stereotypes were laid -- as drunken savages closer to monkeys than humans (I kid you not, that is what the English under Cromwell and into Victorian times saw the irish as).
They didn't impose cruelty on India for hundreds of years -- they only ruled India for 150 years, the first 50 being Company rule. From 1850 until the 1920s there were incidents of cruelty -- some extremely cruel like Jallianwala bagh, but the English had the sense to realise that if they were constantly cruel, they would lose their empire quickly
It is often said that Cromwell visited ‘genocide’ on the Irish, but where is the evidence for this? The most cited example, the butchery at Drogheda, occurred as the result of the Irish Royalist’s refusal to surrender, necessitating the Parliamentarian Army storming the town, taking heavy casualties as a result, and according to the rules of war at the time, the garrison thus had no right to expect quarter. In any case, far from all the people in Drogheda were killed.