The War of the Gargantuas (1966)

In the waning hours of a stormy night, the tranquility of the ocean is shattered as a giant octopus launches a vicious attack on a lone freighter. However, the octopus finds itself outmatched by a grotesque, green Gargantua, which savagely intervenes only to turn its monstrous appetite towards the hapless crew of the ship. The sole survivor's terrified account of the incident to the police leads them to the doorstep of Doctor Paul Stewart and his assistant Akemi, who had previously nurtured a creature eerily similar to the perpetrator. Haunted by the fear that their former ward has matured into this man-eating monster, Stewart and Akemi are thrust into a desperate race against time. The green Gargantua, now known as Gaira, continues his relentless rampage, leaving a trail of destruction and chewed-up clothing in his wake. In an unexpected twist, a second, larger Gargantua, christened Sanda, emerges from the shadows. Dressed in brown fur and towering over 100 feet, this creature is the grown-up version of the one Stewart had in his lab, and it rescues Gaira just as he faces imminent death at the hands of the military's laser assault. Unaware of Gaira's wicked nature, Sanda nurses his 'brother' back to health, setting the stage for an epic showdown. Upon discovering Gaira's sinister character, Sanda is overcome with disgust, leading to a titanic clash between the two Gargantuas that threatens to level Tokyo. The city becomes their battleground, and the once-benevolent Sanda is now the only hope of stopping Gaira's reign of terror. As Stewart and Akemi scramble to save the misunderstood Sanda from the army's relentless pursuit, they must also confront the chilling reality that more Gargantuas could potentially rise from the fragments of these two battling behemoths. In this gripping tale of terror and brotherhood, the War of the Gargantuas explores the horrifying consequences of unchecked growth and the destructive power of sibling rivalry.

The War of the Gargantuas is an action movie featuring Russ Tamblyn.

The War of the Gargantuas is currently streaming for free (ad-supported) on Freevee, Plex, Plex Player, Pluto TV, Shout! Factory TV and Tubi TV and it's also available on Criterion Channel, Max and Max Amazon Channel.