It's an inherent problem of the system that produce douche hunters like that idiot S ranker one. Humans just simply awake to the power, and that power stays (except for exceptions like the MC). So, one day a person with weak willpower will suddenly gain S rank powers. That makes them instantly a superstar in the whole world, with people milling around offering million dollar deals. They can clear quite challenging dungeons with basic training alone due to their personal stats alone. Of course they would need to work hard to take on S level dungeons, and still might have to retreat, but such hard work is a simple and fine way to spend their time, with all the rewards and respect they enjoy. It's easy to image how this will easily lead to a bloated ego and bad behavior.