"Fighting's" comically on-the-nose title is the only remotely interesting thing about it. It's a completely predictable story, acted-out with stock characters, uninterestingly shot and punctuated by boring action scenes. It's a case study in why similarly low-rent films of the past tended to crank ONE element (usually the violence, the sex or a hot-button "hook" theme) up to eleven for saleability, earning the moniker of "exploitation films."
The good guy is Channing Tatum (still well-ensconsed in his niche as the "teen hearthrob for girls who men who look like, well, men") as a homeless(?) Southern dude selling bootlegs in NYC and getting into impromptu street fights with the other riff-raff. Said fights are observed by a pro-hustler (Terrance Howard) who scoops the kid up and introduces him to the world of bare-knuckle street-fighting for cash. You will be unsurprised to learn that the film follows them through a series of fights in various colorful (and escalatingly-wealthy) neighborhoods against area-appropriate opponents (a Japanese hotel/brothel's champion is... A KARATE MASTER!!! Wow! What an angle...) You will be similarly unsurprised when, early on, Our Hero meets the circuit's reigning champ and - whod'a'thunk it? - he turns out to be an Old Rival from his past who recognizes him and taunts him with vauge allusions to the Dark Secrets of where and how he picked up his prodigious punching powers. There's also A Girl, who in accordance with The Ancient Laws of such things possesses The Heart of Gold, The Career of Dubiousness, The Child of Illegitimacy and, yes, even The Grandma of Ethnic Humorousness. This is the kind of plotting that'd make Joseph Campbell eat a bullet.
Now, better movies have been made from worse elements - usually by the aforementioned "eleven-ing" of some tangential attribute - usually the action scenes but occasionally the acting. "The Karate Kid" is novelly-characterized enough to make you forget your just watching "Rocky" again, "Ong Bak's" lead guy can jump nine feet in the air and knee a guy in the forehead, you get the idea. "Fighting," unfortunately, has delusions of serious drama, so it elects not to show off either.
The fight scenes are uniformly bland, the result of going for a semblance of absolute realism: Most of the fights quickly descend into improvised wrestling on the floor, hits to the face usually end things, etc. This worked out fine in "Redbelt" where the "fights" were quick, brutal punctuation marks for interesting drama. Here? You're slogging through knee-deep cliches to get to the fights, and then they're just as dull.
As for the acting... the seemingly upscale casting doesn't end up doing it any favors. Tatum's character is basically Lil' Abner - a stuttering "aw shucks" hillbilly with fists of steel - while Howard is stuck doing his "world-weary-dude-always-on-the-verge-of-bawling" bit; which means that MOST of the film's big dialogue scenes happen between two characters who mumble and half-start through 90% of their lines. It's like watching a pair of stroke victims compete in a Brando impersonating contest.