This movie falls into that special category "Not great, but not as bad as it's reputed to be". It was started by one director, the notorious Sam Fuller, in Spain, but finished by another, the less notorious Barry Shear, in Mexico. The footage shot by Fuller was not used, and his original script was entirely re-written. Officially Lukas Heller was credited for it, but according to Rod Taylor's website, large parts of the script were written on the spot, by Harris and Taylor, who both were very dissatisfied with Heller's work.
In spite of all these rewritings, some of Fuller's original ideas about a once peaceful sheriff who becomes a renegade after the violent death of his wife and child, still shine through. The opening scene with Harris as the legendary sheriff of the town of Santa Rosa, is quite good. Harris has become a legend because he has been able to keep the streets of Santa Rosa clean without using any violence. But his pacifism is one of a peculiar kind: instead of wearing a firearm himself, he has armed all citizens of his community, turning the town into a bunker with one way in, and no way out for those who dare confront its peaceful sheriff. But Taylor finds a way out: while his men are being disarmed, he kidnaps Harris' son, forcing the townspeople to lay down their arms. While the villains ride out off town, the whole affair turns into a tragedy ...
Of course Harris goes after Taylor and his cutthroats, even crossing the border and chasing them into Mexico, where he teams up - every now and then - with a local officer (Al Lettieri) who's also after Taylor. Within the story's framework, the two men are each other's moral counterparts: violent by nature, Lettieri is now forced to work within the law, while the once peaceful lawman Harris only respects his violent instincts. It's one of those hints at character depth, but Harris change from a pacifist into a madman is much too abrupt and far too soon the story turns into a straightforward, bloodthirsty revenge tale. It's only during the finale that the movie seems to recover some of the glory of that remarkable opening scene. In it, the now demented Harris is confronted with a desperate Taylor, who has found his daughter (the only creature in the world he really cares for). The actual Harris is beyond help, but by saving Taylor, he could have saved the image of the man he once was, but instead Shear and his screenwriters opt for a melodramatic, violent conclusion.
As said, the deadly Trackers is not great. It has a few good action scenes, quick and bloody, but the story lacks momentum, especially in the protracted second half. The movie's malignant reputation was probably enhanced by Harris' acting style ('pastiche Brando' as some have called it). Other performances vary: Neville Brand and William Smith (as a lunatic knick-named 'Schoolboy') are always good value, but their parts are either too short (Smith) or ill-defined (Brand) and Al Lettieri is miscast as the Mexican lawman; without a steady directional hand, he turns out to be no more than mediocre actor with a great face. Taylor's casting as a sadistic (but deep down inside vulnerable) villain was surprising, even daring, but he does a fine job, almost singlehandedly saving the movie. Nobody was credited for the score, which is no surprise: it's simply Jerry Fielding's score for The Wild Bunch (1969).