As must always be kept in mind while viewing classic SF cinema, one cannot and should not extricate a film from its historical context. Kronos is no exception. This is 1950's SF movie making at its marginal budgetary best.
Certainly the storyline taxes credibility, involving alien possession of humans, but the ETs at least have a practical purpose for invading than just doing it out of spite. Plus, the dirty work isn't accomplished with sundry flying saucers and blaster rays, but by a huge robot.
The acting is an uneven mixture of serious and melodramatic that oddly adds to the dark overtones of the fims early scenes. The dialogue, littered with quasi-scientific jargon, flows at near poetic tempo.
Ultimately, it is the clever resourcefulness of our nuclear-scientist heroes that wins the day. Now that has to be worth watching!