Yeah, as it turns out Wyll is the least popular character overall because of this;
So, when I learned that Wyll was close to his father, had a happy childhood, and became the 'Blade of Frontiers' through a pact with a devil, he seemed like a foolish person obsessed with the hero mentality.
He is foolish and self-righteous and comes off as arrogant. Also he is a Warlock, which is sad enough in terms of class but worse he is a Warlock who sold his soul to become one which comes off as incompetent or desperate.
As for the use of language it's less shocking in English, but they really should correct the Korean translation if it gives the wrong idea about how vulgar he is. Thank you for pointing that out.