What word is the opposite of established?

There isn't one single perfect opposite for "established," as the word can have different meanings depending on the context. Here are some possibilities, depending on the meaning you're looking for:

If "established" means well-known or recognized:

* Unknown

* Unproven

* Emerging

* New

* Untested

If "established" means firmly set or fixed:

* Uncertain

* Unstable

* Fluid

* Changing

* Volatile

If "established" means set up or founded:

* Unfounded

* Unformed

* Nascent

* Incipient

* Newly created

If "established" means accepted or widely recognized:

* Challenged

* Contested

* Controversial

* Disputed

* Unconventional

The best word to use depends on the specific context and the intended meaning.