https://en.wikipedia.org/wiki/List_of_biggest_box-office_bombs

Nominal loss column.

Will use midpoint in case of an estimation.

Movies with limited theatrical releases obviously don't count if they are designed to make their money from streaming.

Vandalizing Wikipedia is allowed but considered unsporting.

Keep in mind that lots of good and great movies bomb. It's happened before and it'll happen again. I think most people who like movies would probably be able to list a bunch of critically panned movies they enjoyed too.

Edit: Meant to let people submit their own answers, but the market still works. Here's a similar market where you can add your own answers:
https://manifold.markets/asmith/which-of-these-will-be-the-biggest