The opposite of fascism is anti-fascism.
Communism, Humanism, Socialism, Social Democracy, Syndicalism, Anarchism, Pacifism, Republicanism (not to be confused with the Republican party), etc..., may clash with fascism and be mutually exclusive, but they are not the opposite.
There are even liberals, nationalists, and conservatives who would be opposed to fascism.
All those who oppose fascism are anti-fascist. When it comes to that, the more the merrier.