Smooze

The Smooze was a gargantuan slime-monster and the secondary antagonist of My Little Ponies: The Movie - which took place in Generation 1 canon, making it very different from the current series and more in line with what modern audiences associate Care Bears or other "kid-friendly" cartoons to be.

The Smooze was nevertheless a geniunely terrifying being, especially giving the setting it was in - with the ability to grow to gargantuan sizes it spread across all of Ponyvile and buried anything (living or not) in its path, completely ruining the land and turning once paradise-like fields and castles into barren wastelands - it also threw chunks of itself around that when attached to living beings turned them "mean" and "grumpy" (which despite the childish language is actually a more dangerous threat than one might think as removing living creatures' ability to care about each other can lead to apathy and despair).

The Smooze was semi-sentient, able to form hands and faces but only able to express rage and malice - with animalistic roars and grunts - the ponies were originally powerless to stop the beast after the witch Hydia released it, with even the Rainbow being ultimately overwhelmed by the Smooze's power.

Yet just as the Smooze seemed ready to devour the last bit of Ponyville not corrupted by its presence the Flutter Ponies arrived - using their magic they managed to cast the Smooze away and undo its evil before lifting the mass of slime into the air and dumping it back into the volcano it came from along with Hydia and her two daughters.