Formal:
* Kei te whakamiharo koe. (This is the most literal translation and means "You are amazing.")
* He tino whakamiharo koe. (This means "You are truly amazing.")
Informal:
* Whakamiharo koe! (This is a more casual way to say "Amazing!")
* Kei te pai koe! (This literally means "You are good," but can also be used to express "You are awesome" or "You are amazing".)
Other options:
* He tino pai koe! (This means "You are really good!")
* He maia koe! (This means "You are brave" or "You are courageous," which can also be used to express admiration.)
* He tino toa koe! (This means "You are very strong" or "You are very powerful," which can be used to express admiration.)
The best way to choose the right phrase depends on the context and your relationship with the person you are speaking to.