What is the polar opposite of liberalism (philosophical version, not the pejorative)?

So the true polar opposite isn’t just “conservatism” or some current political label — those overlap with liberalism in many ways.
The real opposite is any ideology that rejects individual liberty as the moral foundation and instead elevates collective unity or authority above the person.

Authoritarian collectivism — philosophies that hold that

the individual exists for the group, the state, the nation, etc., and must be subordinated to it.