We should call it a 45

It's a ready-made new method of identifying something that turned out to be a massive mistake, especially if loads of people told you beforehand that it was going to be a huge mistake. Particularly if it's the kind of mistake where you should have known better anyway, where the decision only made things way worse and completely failed to live up to even the most paltry expectations.

"Did you end up buying that old Toyota?"

"Yeah. Turned out to be a real 45."

"Ha! I told you it was cheap for a reason!"

Stuff like that. Or something like:

"I'm going to book this place to stay, looks good."

"Lots of bad reviews, dude."

"Nah, I think it'll be sweet."

"I'm warning ya, that's a real 45."

It's pretty perfect.

"You want to go see that new movie?"

"No, that'll be a total 45."

Let's make it happen. Any examples you can think of where the phrase would already have been useful? (Apart from the blatantly obvious!)