Breaking Bad comes to mind.

I agree.

For some reason, BB always comes to mind. Walter White's real rival was his own ego. Your bad guy doesn't have to be someone, it could be someTHING. It could even be your (anti)hero's flaw.

A Helper is usually the one grounding the (anti)hero or guiding them. His or her opposite, or the voice of reason. They CAN be just as evil as your (anti)hero is, but as opposed to the rival it guides your (anti)hero toward the right direction, also emotionally. Doesn't mean they're right or that your (anti)hero will listen to them, but at the end of the day they want what's best for your (anti)hero.

With that in mind, there's always the option of a twist. Like the Helper has been working for the Rival all along, or they die and the Hero is left to fight alone - by that beating his/her flaw or giving in to it. Use the twist as your reversal.

The reversal could also be the flaw giving way to a new or another flaw. The flaw itself could open new possibilities: Walter White wanted to make SOME money for his family... But then he got greedy, because he was so damn good at it. He pushed his limits, the law's limits, his friends and family's limits.... And then he died for it. For his ego.

Your (anti)hero's story should escalate: the obstacles, the stakes, the flaws, the goals... And the Helper + the Rival work for and against it all.

Can't recall where I read this but it stuck in my mind: When the hero does not improve at the end of the story but continues in his/her same flawed ways, that is a comedy. Of course, in many comedies the hero does change for the better, or at least compromises, a little. An example: As Good as It Gets with obsessive compulsive character played by Jack Nicholson. If comedy doesn't fit your concept exactly, is it a dramatic comedy? a black comedy?

Maybe, by not becoming better in the end, but rather worse, the Hero has an impact on the Helper/Rival, making him/her better?

My feeling is there is nothing wrong with a cautionary tale. Perhaps google "cautionary tale" and see if you can find any answers there - in regard to structure or whatever. Good luck. I was going to Direct a script I wrote and I had a Golden Globe Winning Actress interested as my lead but she couldn't get around the fact that her character was as you describe - gets worse in the end. She decided not to do it, not really understanding what a cautionary tale was. (Even after I explained it to her.) She is quite an experienced and incredible actress and only wanted to do "positive" roles.

Hey, James.
Thanks for sharing your experience :)
Now I'm curious to know if the actress' response to your script made you want to rethink it in any way.

I'm thinking of Midnight Cowboy. As James Ridgley says, that's a cautionary. Still, there's a way out. Your hero could try to redeem herself and fail, but achieve something noble nevertheless. Example, the corrupt alcoholic cop who takes a bullet for-- I was going to say, for the President, but that well is now poisoned.

When I think cautionary tale, I think 'Scarface'. He came from nothing to rise to the top but his own vices/flaws eventually kill him.
The story I'm working on is a cautionary tale. The main character (because you can't quite call him a hero) dies at the end due to not being able to overcome his flaws even with family and the love of his life by his side. He claws his way out of poverty and makes it to the top of a mafia family to shower his people with money and power but then avarice takes over and when those things are taken from him, he turns on everyone. His own people take him out in the end.