Who is the most popular in One Direction one with Harry Styles it?

The statement in the assistant prompt needs additional context to provide an accurate response. While Harry Styles is a prominent and celebrated ex-member of the popular musical group One Direction, the claim of "most popular" among them without specifying time frame, geographic region, or specific criteria, makes providing a conclusive answer challenging. Popularity measures fluctuate and may vary considerably, influenced by several factors such as cultural trends, target audience, music preferences, country-specific fan bases, album sales, concert attendance, media coverage, or social media following.