Godzilla (or Gojira in Japan) is heralded as The King Of The Monsters, and it's hard to dispute that title. In his latest "Final Wars" incarnation, Godzilla is also quite possibly his deadliest ever.
Big G's signature weapon is his "nuclear breath" which has been displayed as having power similar to an atomic bomb. This is amplified at the end of Final Wars by absorbing Ozaki's energy to fight King Ghidorah. Due to his need to consume radiation, Godzilla also naturally emits radioactive evergy. This means just being around him is dangerous, even if he doesn't touch you.
Another ability shown throughout the film (and other movies), is 'Zilla's ability to resist injury. Not only is his hide very thick, but he can heal at very rapid rates. He can also freely roam in and out of water for days at a time.
If he has any weakness at all, it's that Godzilla feeds off radiation, and thus can be lured to it much like an animal will seek out food. But give that Godzilla is also one of the deadliest natrual disasters, this may not be an effective tactic in the end.
"Peace Through Tyranny"
Love, compassion, mercy are words that have no meaning for Megatron. He has risen to the leadership of the Decepticons by a combination of brute strength, military cunning, ruthlessness, and terror. On Cybertron he was commanding general in charge of all military operations against the Autobots, who referred to him as "The Slag-Maker." It was a title of fear. A title of respect. A title Megatron relished. His banishment to Earth has only made him more bitter and more evil-minded, if that is possible. He aches to return to Cybertron and complete his mission of eradicating the Autobots. But while on Earth he is dedicated to eliminating those Autobots marooned here with him- and his plans go far beyond that. He realizes the Earth is one huge stockpile of metal and fuel resources and means to possess it all, with the aid of his fellow Decepticons. But his plans go even further, plans so grandiose even his fellow Decepticons are unaware: Megatron intends to enslave the entire human race. He allows no exceptions to his motto.
Megatron is incredibly powerful and intelligent, the equal of Autobot Leader Optimus Prime. His fusion cannon can convert any small amount of matter into large quantities of explosive nuclear energy. The cannon can fire a blast up to 12 miles and release enough energy to flatten a small town. Megatron can use his internal circuitry to connect the cannon interdimensionally with a black hole, where it can draw on anti-matter as its power source. The blast from this is far greater, but it creates a tremendous strain on Megatron to do this for even one blast.
Megatron has no known weaknesses.
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