I have tried to write two Westerns from that angle and could not get beyond chapter 3. I just could not make the story hold together without a strong hero.
What you could try is rather than a serious villain, make the MC an anti-hero or anti-villain.
An antihero, or antiheroine, is a protagonist in a story who lacks conventional heroic qualities and attributes such as idealism, courage, and morality. Although antiheroes may sometimes do the "right thing", it is often for the "wrong reasons" and because it serves their self-interest rather than being driven by moral convictions.
An Anti-Villain is the opposite of an Anti-Hero — a villain with heroic goals, personality traits, and/or virtues. Their desired ends are mostly good, but their means of getting there are evil. Alternatively, their desired ends are evil, but far more ethical or moral than most villains and they thus use fairly benign means to achieve it, and can be heroic on occasion. They could also be someone or something whose desired ends or means are not necessarily "evil" at all, but their actions simply conflict with that of whoever seems to be the protagonist.
One simple way to set up an anti-villain is to have an MC who has a strong personal moral/ethical code, but one that is seriously at odds with the society they live in.