I had a bad experience with Avis in FRA a few years ago. They tried to trick me into getting a compact.

Me: "I have a voucher for a Toyota Carina."
Avis: "We are out of Toyota Carina. How about Opel Astra?"
Me: "Astra? That's compact. Carina's intermediate. I want intermediate."
Avis: "You see, you're American. Astras are intermediate here."
Me: "I used to live here, Opel Vectras are intermediate, Astras are smaller. Gimme the manager!"
Avis: "Fine, we are out of all intermediates. We'll give you Omega then. There's extra charge."
Me: "For WHAT? Gimme the manager!"
Avis: "No, no charge, you can have the Omega."

The point is - she lied to me. Since then, I have rented from Sixt or Europcar. Never gone back to Avis.