FINALLY, I have become the guy on medium. I felt so happy last night when I did. Crazy awesome feeling.
Unfortunately I can't provide a screenshot, though, or my kill count. I started I Wanna Be the Guy last year and got to the final boss, then my hard drive on my laptop crashed, so I lost my save file and all. Yesterday I decided to use that save fix program to skip back to the final boss and to give beating it another shot (heck if I was going to go through the entire game again just for the final boss), and I beat it last night after 2 solid hours of fighting him. I didn't really care to watch all of the credits, though, so I exited before they were over and it didn't record it as me having beaten The Guy. Technically I could fight him again to get a screenshot, but I don't feel like spending another hour fighting him just to get a screenshot.

Doesn't matter, though. I beat him and now I can finally rest easy knowing that I'm the newest Guy out there.
Actually, I remember fighting the guy last year and thinking I'd never beat him in a million years. Now that I've come back to it after beating games like I Wanna Kill the Guy and getting to the final boss (still working on beating him) of I Wanna Be the Boshy, I think my skills have improved so much that the final boss of I Wanna Be the Guy really isn't too tough. It's just one of the longer fights. Kind of interesting how playing spin offs have made me better at the source material.