With rare exception (109F, Spit V) the early war planes aren't going to be able to compete, 1 v 1, with the late war planes. So, on the assumption that our Floob meant "which of the late war planes is the worst," I will nominate the FW190-A8. I have tried, for years, to fly that competitively in 1 v 1s, and have yet to discover a way to make it work. That hasn't been true (for me, at least) for any of the other late-war planes.
- oldman