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Nightmare Fuel: Dragon Ball GT
Baby. Basically a more family-friendly version of the Thing, Baby is a supremely vindictive mutant parasite that infects all but a tiny handful of people on Earth, taking complete control over them, and when he picks a main host body his power warps it to completely unrecognizable levels while enhancing its abilities. Even worse was that in his earliest stages instead of controlling people he infected he ate them, wiping out entire spaceships full of passengers.