This setup suggests that “Fresh” is a slice of violent urban realism. Not quite. As Fresh witnesses the destruction of those he loves, he decides to fight back, using his analytical chess-whiz mind. Pitting bad guy against bad guy in a disinformation campaign as elaborate as Dashiell Hammett’s “Red Harvest,” Fresh becomes a pint-size combo of Superfly, Bobby Fischer and Dirty Harry. Suddenly we’re in an action-movie fantasy, and it’s not easy to swallow. It takes nothing away from young Nelson’s watchful, poised performance to say that Fresh himself is bogus. From scene to scene he’s whatever the screenwriter wants him to be; by the end, he’s no longer flesh and blood. Though well acted, and handsomely shot by veteran Adam (“Midnight Cowboy”) Holender, “Fresh” sacrifices real emotion for thriller contrivances. It’s a tourist’s drive through inner-city hell.