I finished Dead Days recently and got all caught up to HIVE last week and now I'm interested in reading more manga/webtoons with similar cool older (Age 50 +) male leads or plays a major role in the storyline.

They don't have to be horror or thriller, romance is also fine (but I think I've read all the May-December mangas) as well as sci-fi and drama.

Thanks in advance!

Inuyashiki the main protagonist is middle age, working class man.
Hito Hitori Futari the main male protagonist is Japanese Prime Minister.

Thanks so much, I've added them to my list. 😃

Oyaji should fit, the main character is the badassest of all the badass old men in manga.

You're looking for badass old men? Then you need to read Oldman! 🤣

Haha, holy crap that cover art is good though.

Ping Pong Boss is great so far.

Bokko: Follows an old general/strategist during a siege in ancient China. I thought he was pretty badass.