NEUTRON VS. THE KARATE ASSASSINS is the last and least of the five-film Neutron series. This one is the most obscure of the lot, as it was never syndicated for American television which means that there's no dubbed in English version as far as I know. In any case, it feels like interest in the Neutron films were waning by 1965 because this is strictly run of the mill fare, lacking the excitement of the previous instalments.
Prolific director Alfredo B. Crevenna returns to helm a tale that cashes in on the then-booming craze of the 1960s, karate. An arresting opening sequence sees these karate assassins utilising their skills around the globe, wreaking havoc in both Paris and London. Before long the Mexican cops are on the case and Neutron gets called in to help out. There are a lot of mild comic antics which take place in the local gym but there's also a lot of talk and padded song and dance routines (from a group called the 'Gay Crooners').
Series stalwart Wolf Ruvinskis does turn up for a few fight scenes but they do feel rather brief unlike the extended bouts we saw before. It's only at the action packed climax that things really pick up. Other than that my favourite scene is where one of the assassins is captured by the cops and chooses suicide over spilling the beans. Prolific Mexican character actors German Robles and Carlos Lopez Moctezuma play in support, but this is still a lifeless effort with too much detection and too little wrestling.