What is the Shawnee word for Great Spirit?

The Navajo do not use the phrase "great spirit" . Although I could give you a literal translation, I think you mean the Navajo name for the monotheistic Christian God. That Word is: Diyin Ayóí Átʼéii

God in the Navajo religion, meaning a supernatural being is: Haashch'ééh

A male god is Haashch'ééh biką'. Female is Haashch'ééh ba'áád.

There are many different important deities in Navajo thought and they all have their own names.

The marks above vowels are high tone marks, they change meaning as much as having a different vowel.

The marks under some vowels mean they are nasalized..

The Ch' and t' sounds are glottalized consonants, they are different than regular ch and t sounds. The mark between after the ba in the last Word is a consonant called a glottal stop, We have it in uh'oh.