Wasn't Marx, he was long dead before fascism (he also didn't write too many handbooks on how communism was supposed to actually work), it's okay though because it was this humanitarian named Joseph Stalin. (Technically it was apparently Georgi Dimitrov but nobody knows who any Bulgarian is.) Before "fascism", Lenin was pretty big on labeling any opponent an "imperialist" (still a common nonsensical epithet on the Left, see Twitter for examples) but he didn't really live to make the switch. (edit: To be fair, Lenin was probably the smartest Communist so he might have come up with something better.)