So, some thoughts beyond just the synopsis:
The World After The Fall - This style of action series is very common among webtoons, but this one does it better than most with a protag who doesn't dick around. Very much a, 'nah, fuck that noise, ima stab you now,' kind of guy.
Return of the Mad Demon - Martial arts with a take-no-shit protagonist who is...perhaps a little off his rocker. Really a FAFO kind of main character.
The Stellar Swordmaster - Just a solid dark fantasy. It's not brutal in the way of Berserk, but it doesn't shy away from some of the more unseemly aspects of a medieval fantasy setting.
Myst, Might, Mayhem - The protagonist is brutally pragmatic. Evil, even. But there's no mustache twirling and somebody else almost always starts it. It's an interesting change of pace.
The Knight Only Lives Today - Groundhog Day-esque timeloops. Fun, good fight scenes, interesting cast.
Bad Born Blood - This one has been developing an interesting setting where the MC has to deal with a '...are we the bad guys?' revelation and it's not pulling any punches on that premise. One of the better series I've tried so far this year.
The Regressed Mercenary Has a Plan - So, yeah, it's yet another regression plotline. The big selling point for this series is that the fight choreography is phenomenal.