Thatcher for me. She did so much damage to communities and to the country. The decimation of industry is harming us now, so many years later. I don't think she meant so much harm though, I think she lacked imagination and empathy, and was unable to conceive of a different result to the one she intended.
For instance, she thought that selling council houses to tenants would result in most people owning their own homes, which she saw as very desirable. She was unable to put herself in the shoes of people who were better off with a secure tenancy and a reasonable rent, and unable to imagine that the houses would be sold on to private landlords and be rented out with much, much higher rents and less maintenance, which is what has actually happened.
She thought that privatisation of utilities would lead to greater competition and lower prices, she was unable to imagine that other governments could end up owning our utilities and charging what they like, which is what has actually happened.
Just too blinkered really.