Definitions:

1. The quality or state of being final, most fundamental, or unsurpassable in degree, importance, or truth. NOUN
   • In many religions God is regarded as the ultimateness of existence.
2. The state or quality of being the best, greatest, or most extreme of its kind. NOUN
   • The ultimateness of death gives meaning to the choices we make in life.

Synonyms:

• absolutness
• finality
• fundamental nature
• supremacy
• ultimacy