Who do you think is the most badass character in all of manga and anime?
Personally, I think Guts (Berserk), Hiruma (Eyeshield 21), Alucard (Hellsing), Zoro (OP), Kamina (TTGL), Spike (Bebop), and Takamura (Hajime no Ippo) fit the definition of badass pretty well, but none of them can rival Onizuka:
http://www.onemanga.com/GTO/122/16/