I'm sorry but your tree is beyond saving. It is past dying and is well and truly dead.

I scrapped back the bark and it is still green on the stem which is why i had hope 🙁 not to worry. thank you

TOO DRY, maybe too hot depending on the location. Magnolia grandifloras are generally EASY, even in a container. I introduced them into my NJ yard years ago and now they grow like weeds.

are you posting from Australia? It's Winter there now right? Educate me, what was the winter like so far?

What kind of heat was it exposed to in your Summer? Hot dry winds could cause this if the soil is dry. In the Americas, they grow natively in areas with 40-80 inches of rain a year, hard to overwater one in a container, in Australia. (There is no place in Australia that would cold burn this way in any Australian Winter, ever.)

If you have a dead plant, it's a good idea to take it from the pot and have a good look at it.