If it made it into theaters, then there was enough of a budget and decent test audience reactions. If it went straight to DVD (nowadays straight to streaming/on-demand), then it likely is terrible.
So depends on your criteria. There are YouTube channels that just react to terrible movies, and it’s fun to watch.
Cannot always tell. I remember watching Kiss the Girls and thinking it was pretty good, but the ending kind of brought the whole experience down.
I later heard interviews with those involved in the movie. The original version departed drastically with the book ending. And that ending caused all test audiences to give an ultimate thumbs down in the last few minutes. They made two more endings. One where the movie people used some of their "creativity" to improve on the book ending. And one based on the book ending. Audiences didn't hate the new creative take as much as the original, but still didn't approve. The test audiences were over 90% about the book ending made into film. Nevertheless they didn't go with the book ending. They valued their creativity too much. Isn't the first time I've heard of movie makers going against test audiences.
BTW, Battlefield Earth had three recognized actors, and a budget of $93 million including $20 million in marketing. Still made it to the screen.
Here is a partial list of awards for various kinds of worsts this film has garnered.