Isekai / Reincarnated TRASH [DO NOT READ!!]

Harem, Polygamy
https://www.novelupdates.com/series/shiro-no-koukoku-monogatari/

Axed/Cancelled/Discontinued
https://www.mangaupdates.com/series/1c2tgip/shiro-no-koukoku-monogatari

Ecchi (not good story? based from tags)
adapted to anime
https://www.mangaupdates.com/series/k15ld70/sentai-red-isekai-de-boukensha-ni-naru

https://mangadex.org/title/d7f927c8-c1f5-474e-bb3d-57da04be7662/sentai-red-isekai-de-boukensha-ni-naru

Harem, Polygamy (world building but tags & plotholes destroyed it)
https://www.novelupdates.com/series/fushi-no-kami-rebuilding-civilization-starts-with-a-village/

https://www.mangaupdates.com/series/9zcfajt/fushi-no-kami-henkyou-kara-hajimeru-bunmei-saiseiki

Harem, Polygamy
https://www.novelupdates.com/series/entering-a-company-from-another-world/

https://www.mangaupdates.com/series/swojs0t/isekai-kara-no-kigyou-shinshutsu-motoshachiku-ga-isekai-tenshoku-shite-nariagaru-yuusha-ga-kouryaku-dekinai-meikyuu-o-tsukuriagero

Ecchi, Harem
based on novel
https://www.mangaupdates.com/series/w8woai0/isekaigaeri-no-yuusha-ga-gendai-saikyou

Harem, Polygamy
Adapted to anime
https://www.novelupdates.com/series/i-got-a-cheat-ability-in-a-different-world-and-became-extraordinary-even-in-the-real-world-ln/

https://www.mangaupdates.com/series/749t9kn/isekai-de-cheat-skill-o-te-ni-shita-ore-wa-genjitsu-sekai-o-mo-musou-suru-level-up-wa-jinsei-o-kaeta

Based on harem novel spin-off
Main story adapted to anime.

https://www.novelupdates.com/series/the-deeds-of-an-extremely-arrogant-villainous-noble-ln/

Harem
https://www.novelupdates.com/series/using-the-faulty-skill-escape-i-strive-to-become-the-strongest-one-starting-from-the-utmost-low-end-of-ability-levels/

Incomplete Due to Author/Artist Death
https://www.mangaupdates.com/series/syshndg/hazure-skill-nigeru-de-ore-wa-kyokugen-tei-level-no-mama-saikyou-wo-mezasu

reverse dungeon isekai

Final Chapter: Chapter 18

Harem, Polygamy
https://www.novelupdates.com/series/i-was-reincarnated-as-the-older-brother-of-a-villainess-destined-to-die-so-i-want-to-change-the-future-by-raising-my-younger-sister-with-my-own-hands-i-am-the-strongest-in-the-world-but-my-little-s/