it doesn't really have to be that realistic, as long as it is logical or explained with reasons that's not utter BS. Has to be serious novel, at least it has serious plot and goals. would be better if it has unique power system such as Hero Academia quirks or LOTM, different superpowers even if you're weak if you use your power correctly you can kill someone stronger. it doesn't have to be level system "I'm one level/stats/cultivation higher than you so I'm stronger!" but I'm also ok with it. thanks!
The Melancholy of Haruhi Suzumiya The Way of Kings The Perfect Run There Was No Secret Evil-Fighting Organization (srsly?!), So I Made One MYSELF! (This doesn't fit your requirements, but give this one a try. MC just wants life to be fantastic instead of boring.)
Well if you are fine with main stream novels the Sandman Slim Series by Richard Kadrey And Low Town: A Novel by Daniel Polansky Are quite good.
If you don’t mind immersive fantasy, then I suggest Trash of the Count’s Family. It has excellent internal logic. The goal is to live a lazy life, but an amazing amount of stuff has to be done to reach that goal.
The Great Storyteller - mc is a miserable author who got reborn to the day his first novel got popular. Characters are interesting but at the same time realistic. Tho there isn’t any fights nor powers. Mc have a unique ability that allows him to master any language as soon as he reads it which is the only unrealistic thing along with him being a reborn. It’s really interesting so I recommend checking it out!
The emperor's soul by Brandon Sanderson Realistic ✓ (as realistic as fiction gets at least) Serious ✓ Goals/Motivation/stakes are clearly communicated from the start ✓ Unique power system ✓ (its brandon after all) And so much more!