What is another word for Unstoppable?

Here are some words that can be used as synonyms for "unstoppable":

Formal:

* Irresistible

* Invincible

* Indomitable

* Impregnable

* Insurmountable

* Uncontainable

* Inexorable

* Unbreakable

Informal:

* Unbeatable

* Powerhouse

* Force of nature

* Juggernaut

* Rollin' (slang)

* On fire (slang)

The best synonym for "unstoppable" will depend on the specific context in which you are using it.