I can't think of a comic book artist who's stylistic trajectory during their career is as extreme as Mike Mignola's. Usually, comic book artists have three phases of their careers. The first is when they come on the scene with a lot of fire, passion, and raw ability, rough edges that need to be sanded. In the second phase, they enter a refined phase where they achieve their creative maturity. This is usually at the height of their powers and they do their best work. The third phase is when they've been burned out by the rigors of the craft. They start to cut corners. Their work takes on an air of laziness and lack of interest. The fire is gone. But with Mignola, something else happened. He invented a whole other way of cartooning. I also can't think of any other comic book artist who's done this, actually created a whole new visual language for comic books. Not only did he create this new approach, verging on abstraction, but he also wields it with such mastery no one else could ever use the same approach without it being a blatant ripoff.