Tough

Tough is a manga by Tetsuya Saruwatari about a martial artist named Kiichi Miyazawa who strives to get stronger and ultimately defeat his (evil) uncle.  Tough is actually the second of two series.  The first series, High School Exciting Story: Tough, dealt with the character in high school as he learned his family's secret martial arts style.  Tough takes place when the character is 19 and fighting in an underground circuit.

The piece of artwork posted in the post celebrating 100,000 visitors came from this series.  This series is also the inspiration for the anime Shootfighter Tekken.  I really like the color artwork for this manga and, more importantly, how freaking huge the main character is. 

Viz Media is releasing the manga in America under the name Tough but I'm not sure if it's the first or the second manga series.