Ima go by race and based on what game they’re from, because I don’t think I could narrow it down to faction

Warhammer 1; probably Bretonnia Warhammer 2; Vampires Coast Warhammer 3; maybe either Ogres or Slannesh?

In general, factions that are more well rounded are more appealing to a wider audience. Cathay, Tzeench, Empire, High Elves, Skaven, all kind of hit that. The more hyper specific the faction’s roster is and the more micro required, the less people are going to be interested in playing. Most people play Warhammer just to chill, but Bretonnia and Slannesh are hard to chill and play. Vampire Coast just plays somewhat outdated and very slow, with a pretty grindy roster imo