-Goes into demon form-
A re-occurring mistake you make in your characters is the oversized trapezius muscles. Lets take a look at a redline I've provided.
As you can see, its almost as if BagHead Kid's neck muscles go all the way up to his jaw line. This happens a lot in your drawings of him, just at different angles. I decided to only use this example of him though. Just easier to critique.
In the reference I got off posemaniacs to the right, he has muscles. He's a fit man. That doesnt mean his Trapeziusessess are gonna be like a Body Builders. I think since you have been drawing these muscles so large, its also distorted the length of the neck. Trapezius are slender unless they're being flexed like;