Sinster Super-Weapons of Savage Supervillains

Kru-El of Krypton-One and Vandal Savage of Earth-Two mirrored one another in both their tenacity for survival, and their sinister scheming minds. Each were threats to their worlds' Kal and Kara... the Supermen Kal-El and Kal-L, as well as Kara Zor-El aka Supergirl and Kara Zor-L aka Power Girl, not just because they had superhuman abilities comparable to Kryptonian cousins, but their lack of morals meant they were unrestrained in cruelty and cunning.

Kru-El, himself a cousin of Kal and Kara, was imprisoned in the Phantom Zone when it was learned that he was developing forbidden destructive weapons to further his evil ends. These devices were placed in a box that was jettisoned to Earth-One. Upon being released from the Zone along with fellow criminals General Zod and Jax-Ur, the trio betrayed the Kandorian woman Lesla-Lar who freed them, and proceeded to use these against Supergirl. Among the weapons were a force-field beam, a disintegrator, a plant scourge ray, a mind-over-matter machine, and a time-reversal ray. Even equipped with these, the tyrannical trio was defeated by Superman, Supergirl... and Lex Luthor, aiding his foes in order to save his sister Lena from imprisonment in the city of Kandor.

Vandal Savage, while himself brilliant in strategy and in some sciences, relied on the equipment of his former teammates in the Injustice Society. Seeking revenge against the Justice Society, who had defeated he and his allies, Vandal utilized a wide-array of his cronies' creations, including:

Brain Wave's immobility cube

Thinker's heavy-ray beam

Per Degaton's paralysis beam

Their monitoring devices

Savage had himself developed a specialized suit, allowing him to fly. And years later, when facing the Justice Society on his robotic world of Colu-Two, Vandal developed equipment that transferred Power Girl's superhuman abilities to himself, in order to battle Superman with the goal of robbing the Man of Steel of his own abilities. These and previous schemes were hatched with the goal of restoring Vandal's immortality, which was slowly wearing off during the 20th century.

On an earlier occasion, Savage used these devices to manipulate the Flash of both Earths into drawing the meteor that granted him immortality centuries ago back to him. However, the result was transforming Vandal into a phantom on his native Earth-Two for a time.

Kru-El and Vandal Savage would return time and again to threaten humanity while seeking power and control. During the course of their crooked careers, as has been noted, they would rely upon their alliance with the Phantom Zone criminals and Injustice Society colleagues. 

In fact, it was two of the Injustice gangsters, who sent Vandal to Earth-One with the goal of changing that worlds history, which had it been successful (which it had, until that world’s Superman changed it back to normal) would've insured the Justice Society had another world to exploit. In addition, a revised history eliminating their other foes the Justice League of Earth-One would've have secured their supremacy over Earth-Two in the 1970s when they with writer turned supervillain Cary Bates had decisively defeated the Justice Society.