What are some one off characters and storylines that a DC Cinematic Universe should NEVER follow or adapt?

To me it was just obvious, that Snyder wanted to do the Death of Superman scene, but the scene was not dramatic at all, considering the fans already knew that from the comics and from common sense that he would have a knock-off resurrection like that of Jesus. Something which does not affect the audience, should just be ixnayed in my opinion. Snyder wasn't going to get the reaction that he wanted. It seems to me that there was a bit too much reliance on familiarity, and then what was changed wasn't for the better. When changes are created, it should always be for the better. Like the old saying goes, called words of wisdom: if it's not broke, then don't fix it.... or even better if it's not broken, then don't break it. If something is poor and needs improvement, then by all means make it better, but when something works well, don't break it. Unless something can be improved, don't make alterations just for the sake of making alterations.

Though I'm not quite sure what you mean by one off though, as the online meaning is: A one-shot or one-off character is a character who appears in only one episode of a series, after which they are never seen again.

Plenty of characters in DC comics could qualify as not being regular characters. Maybe you can elaborate though.

JLA in the early 70's had a character the JLA wouldn't accept because he was too brutal.

He would hit criminals in the face with a tire iron, monkey wrench, etc. not caring how bad he hurt them or even killed them.

Soon after the JLA turned him down for membership, he was murdered by criminals.

Although in my opinion, these are characters that should be spotlighted in cinema, at least once.

And as with Superman, I don't think Doomsday could ever be truly dead.