Sepsizilla is a bootleg Sepsis Bootnokk created by KoopaGalaxain, originally as his April Fool's Day Joke for 2016. While Sepsizilla, originally named as Repurposed 'OC' was never meant to be taken seriously, he was later included in the Fan Made Kaiju Wikia's collaborative series Council of Creators, and appears during Season 2 as an 'evil' version of Koopa manufactured by Aetherium.
As an April Fool's Day Joke, Sepsizilla is essentially a bootleg of Sepsis, proving its status as a Bootnokk even further. Sepsizilla is basically a red and black version of WeegeeZilla, but with Sepsis' horns and tail spikes. As a passing reference to the strange side of the Undertale fandom, Sepsizilla possesses a glowing blue eye and long teeth that create a pronounced 'grin'.
As part of his recruitment and modification by Aetherium, Sepsizilla was given a set of additional abilities by the sentient super-galaxy.
Solar Repulsor: Sepsizilla is able to generate huge amounts of heat and release them in pulses. While the heat given off is somehow unable to set objects on fire, it can easily knock enemies down. This ability was given to Sepsizilla by Aetherium after being recruited.
Aetherium Booster: Sepsizilla can call on the power of Aetherium to restore his health.
The existence of this Kaiju as anything more than a joke was suggested to me by Cdrzillafanon.
And here we have it, people. The most cringy thing in my library. Fortunately, he's been rescued from the scrap heap for the COC series!