The Enforcer (1976), directed by James Fargo.
The series nose-dives into comic buddy cop territory. The plot is weak and the villains feeble: revolutionaries with hippie headbands, a dim psycho-killer, black militants, a radical priest and a pushy feminist bureaucrat, and the usual slimy politicians and police superiors.
Many absurdities: tough guy Big Ed Mustapha crumples when Callahan threatens to report him for having stolen hotel ornaments in his office. Harry menaces a pornographer with a toilet plunger.
Brief nudity, much bloodshed. Jerry Fielding score; I think a proper Dirty Harry film requires Lalo Schifren.
Available on Blu-ray. A relaxed commentary track by the director has a few good bits:
The hostage-taker kicking Eastwood in the butt was unscripted.
They put some green light on Tyne Daly's face when she watched the autopsy.
I understood him to say there are no soundstages in the film: everything is on location.