Honestly no one nature is the best. It entirely depends on what Pokemon you are using lmaO. Diff mons will benefit from different natures; it's honestly dumb to say that a specific nature is the best one because not every Pokemon is going to benefit from a specific stat being raised. As for neutral natures, generally they're nice in a regular playthrough because you don't have to worry about an important stat being lowered. Regardless, neutral still isn't best for all.