Do anyone know of a manga(fantasy preferably) where the mc is a faction leader like overlord?
@D3m0z
Overlord is my top 1 japanese isekai, hard to best that one, but I recommend some others:
https://mangadex.org/title/15553/tensei-shitara-slime-datta-ken - obligatory mention as it is mainstream with well-earned success, good story, good art, even gained anime adaptation. Also, people say the novel is even better
https://mangadex.org/title/23277/maou-sama-retry - bit weird but still decent
* https://mangadex.org/title/34605/release-that-witch - this one I've read the 1495 chapters of the novel and it's amazing, but I've never read the manhua to get a grasp of its quality
Not faction leading but still relevant to world building, kind like MCs of RPGs:
https://mangadex.org/title/20741/gaikotsu-kishi-sama-tadaima-isekai-e-odekake-chuu - I highly regard this one, but people who read the novel say that the manga is worse and don't make justice to the story, chopping off some relevant details
https://mangadex.org/title/12672/tate-no-yuusha-no-nariagari - I'm not a huge fan of this one but hit the mainstream with an anime adaptation
Last but not least, search tool is your friend:
https://mangadex.org/genre/41
Sort the way you prefer, check some out and be your own judge.