Heaven is fair and gives every being unlimited potential. No bs god-envied bloodline where the inheritor can cultivate 10x times faster than everyone else. Equality of Opportunity, everyone can become a Deity if they are diligent and enlightened. Does such a xianxia/xuanhuan novel exist?
Immortal Mortal would probably be a good option. The story is basically about starting with a severe disadvantage but still finding a way through. While he become stronger through various means , I don’t think there was ever an unfair advantage
Basically any novel I can think of ever by IET, I'd recommend https://www.novelupdates.com/series/the-desolate-era/ where the heavens completely fair, the worst you could accuse it of is that that karma isn't intelligent and can only figure out what people are most immediately responsible for somebody's death and not the person who ordered / orchestrated it, though that only comes up once.
I don't read Xianxia, but isn't this super common in basically every other genre? From what I've read so far, the biggest advantage of the protagonist is knowledge, and this magical potential plays a pretty small role overall. Admittedly most of the books I read aren't about fighting abilities, but it's still important in a fair number of them.
They need extreme luck to survive their constant death seeking. Most worlds aren't really that deadly. And after becoming a Deity, they'll leave behind some children. These children start with the ability to utilize external Qi, and thus can cultivate 10x times faster than everyone else. Over time, these children will dominate every sect, and techniques suitable for regular mortals will be abandoned and forgotten. In the end, people without immortal ancestry will be seen as trash not worth investing into.