Trump did some things I liked, and a lot of things I despised, but this was the absolute worst. Convincing Americans and much of the world that U.S. elections are illegitimate. Drive through some red-neck towns and you'll still see "Trump Won" flags still flying. Putin absolutely loves it... Russian elections are of course totally rigged and Russians know it, but this makes it more palatable to them. It implies "see, democracy doesn't work. They're equally as corrupt."
I used to say Obama was the worst President I ever had in my lifetime, but Trump has taken over that position - and I voted for that piece of garbage. I can admit when I'm wrong. Way wrong.