Plot is fine if you ask me and the "can't kill him" is actually pretty funny. The guy was super OP so it makes sanse (reminds me of Joker and batman lol). And he didn't make villains good guys, that happaned only once with future assassin guy.
You are obviously missing the whole point of the story here. If you can't tell the story is going into a direction where the mc's life changes after rebirth and will probably ultimately lead to a very different life than him becoming a villian. The story is about how everything can change and about interpersonal connections and their effects. Panlousi was obviously not happy in his other life, but I guess you only care about big explosions...
MC cannot kill one dude for 20 years??? that's just ridiculous! And then he accidentally turns villains to good guys?? hahahaha this plot is so shit, but art and action is not bad though