The Spectacular Now
There's not really a "bad guy" in the book who tries to hinder Sutter's efforts. Mr. Aster just wants him to pass math, and honestly Geech is probably just looking out for him, too. So what force is actively working against Sutter throughout the book, and even wins in the end? Whiskey.
Whiskey keeps Sutter from following through with plans, from taking his future seriously, and from maintaining relationships. And it's the same demon that took his dad away from him, too. So, yeah. Whiskey's the bad guy here.