I have a few thoughts.
1. Why do you want to draw a line at all?
This comes down to why you write. For me, I have a few stories in my head that want to be written. If I could complete a story that is popular enough to sell, great but it's not why I write and it won't drive what I write.
On the other hand, if your motivator is $$$ then you have to draw the line and put your effort into what will sell, but you have lots of competition.
2. One of my in-progress stories, has a main character who is not a hero, an anti-hero or a villain. I conceptualize him as an anti-villain.
He has a strong moral code but it differs strongly from society at large in many important aspects. The primary conflict is not against a hero, but a true villain.
The MC has a male dominant world view a a secondary mind control power.
The villain is a female mastermind bent on world conquest and the creation of a female dominant society of her own design.
At first she is only aware of the mind control after he stumbles into and takes out one of her operatives, seeing him as a fly to be swatted. In time she learns the true nature of his power and sees him as an existential threat to her goals.
At that point she faces the crisis of leading a secret society directed at world conquest, not by military force, but by infiltration and subversion while trying to eliminate one man powerful enough to be almost unbeatable.
3 From a reader perspective I am a fan of Sherlock Holmes style mysteries, where the conflict is not a physical conflict of life or death, but a conflict of intellects, a conflict of deceiver vs diviner.
As an author or a reader, I don't see a problem with alternate forms of conflict if they are well presented and interesting.
I have another story I have started but not posted. This one I don't intend to post until at least the initial book of the saga length story is complete.
The initial MC is a young male with a very strongly male dominant world view who obtains god like power at the beginning of the story. There will be some traditional conflict in the story, but beyond the first book, the primary conflict is the world view of the initial MC vs the initial world view of society and how society and governments are forced to adapt to him.
The primary limit on the MC's power is range and area of effect. In a small space close to his center he is nearly omnipotent. However. How much he can change things falls off drastically with distance/ volume(space and time), like gravity.
One aspect of his power is passive, his mere existence will constantly push the world around him to be closer to what he thinks it should be.
He is effectively immortal, like Obi-Wan Kenobi, even if someone could find a way to destroy his physical human body, that would only make him stronger.
The world view vs world view conflict is expressed in another aspect of his power. Having followers, having other people adopt his world view/ethos increases his range. Both his passive and his conscious uses of his power can push harder on a larger chunk of the world.
Ultimately the only way to "defeat" him will be to campaign for an opposing world view to keep his number of followers confined. I haven't yet decided if the preexisting world leaders will figure this out before it's too late.
I haven't yet figured out if I can make this work as well on paper as it works in my head.