Plsssss

-The beginning after the end
-Omniscient Readers Viewpoint
-Solo Leveling
-God of Highschool
-Tower of God
-Lumine
-Rebirth
-Demon Slayer
-Jujutsu Kaisen

All of them have boy mc w fantasy and action :)

Eleceed

1> '20th century boys', its not exactly fantasy and or action but bit of Si-fi and has almost no romance. It's a classic and also my 7 star favorite!
2> 'golden kamuy' most entertaining manga ever.
3> 'Tokyo Ghoul' well, you've probably heard of or maybe even read that already. but had too include this anyways.

well, there's also
4> kimetsu no yaiba
5> shingeki no kyojin
6> solo leveling
7> god of highschool

These are all action and fantasy. But, the ones above are my favorite.