@Kyyrito
manga/manwha with a strong mc with a decent romance sub plot
That's a pretty loose description. Some examples would probably help.
If you mean "strong" literal:
https://mangadex.org/title/29231/shin-no-nakama-janai-to-yuusha-no-party-wo-oidasareta-node-henkyou-de-slow-life-suru-koto-ni-shimashita
https://mangadex.org/title/62/ares (very long winded epos, with the MCs romance developing very slowly)
https://mangadex.org/title/282/wolf-guy-ookami-no-monshou (Careful with this. Some people, myself included, call it a masterpiece. But it also contains graphic rape and violence.)
https://mangadex.org/title/8532/grisaia-no-kajitsu-sanctuary-fellows (Haven't actually read this yet, so don't know if it's 1x1 or harem. In the source material VN, its 1x1 and some of the best written romance I know.)
https://mangadex.org/title/20523/beastars
https://mangadex.org/title/1768/all-rounder-meguru
https://mangadex.org/title/1417/shingetsutan-tsukihime
If you're also interested in stories where the MC grows strong, I'd also recommend these:
https://mangadex.org/title/486/
https://mangadex.org/title/916/holyland
https://www.webtoons.com/en/action/girls-of-the-wilds/list?title_no=93
https://mangadex.org/title/1714/kara-no-kyoukai-the-garden-of-sinners
I've got two more that might be interesting, but they are romcoms where the MCs strength is only comically used:
https://mangadex.org/title/34198/yankee-kun-to-hakujou-gaaru
https://mangadex.org/title/28471/kitsune-spirit