She was a forceful demagogue who didn't like consensus or listening to people with differing opinions, who saw the world purely in economic wallcharts, with a habit of guinea pigging potentially unpopular policies on areas she felt disposable like Liverpool or Scotland. Her actions made a few thousand odd folk much richer, but destroyed entire towns worth of jobs for working class people, some of those areas have never recovered to this day. Her inability to talk in anything but partisan politics also badly damaged the British political system.
She was a charismatic force of nature with a political philosophy which encourages market forces but leaves vast majorities of working people worse off.
I think that's a start.