Well, the truth is that there is already another club for badass characters. But there "badass" is understood as "people that are smart/cool/strong/etc.". I personally think that the ideal badass character is just the way he is and is not trying to do anything about it. Other just have to live with it. He is a completed character, secure in his beliefs and confident in his actions. Not some over intelligent otaku (L), not some guy that drowns in his own power (Light), not even an ex failure that found new strength and want to boast about it (Kazuma). Examples for badassness are:
Tawara Bunshichi - Ten Ten
Takayanagi Mitsoumi - Ten Ten
Alucard - Hellsing OVA
Hermit/Tanimoto Natsu - HSDK
Odin - HSDK
Sakaki Shio - HSDK
Jack Rakan - Mahou sensei Negima!
Teressa - Claymore
Miria - Claymore
Sephiroth - FF
Crimson Alchemist/ Zolf Kimbley - FMA 2!
Major General Armstrong - FMA
Furer King Bradley - FMA
Doppo Orochi - Grappler Baki
Hanma Yuujiro - Grappler Baki
Kouga Gennosuke - Basilisk
Kouga Hyoma - Basilisk
Zodd The Immortal - Berserk
Skull Knigt - Berserk
Gutts is a pussy compared to them, so don't expect him here :D
Balalaika - Black Lagoon
Yamamoto - Bleach
Zaraki Kenpachi - Bleach
Assasin - F/SN
Lancer - F/SN
Cornellia - Code Geass
Toujou - Code Geass
Ryuk - Death note
Munsu - Shin Angyo Onshi
Black Star - Soul Eater
Justin Law - Soul Eater
Eibon - Soul Eater
Gunslinger/Father Tres - Trinity blood
Hugue Watteau - Trinity blood
Mihai Mihaeloff - Dogs
Haine is just a psycho, not a badass.
Same for Badou.
Shin - Eyeshield 21
Kongou Agon -Eyeshield 21
Miamoto Musashi - Vagabond
Roronora Zoro - One Piece
Since I have a life I am stopping for now and I will continue later. If you want a badass in the list to be added or removed write in the comments.