Total, Complete, Utter
* Adjectives: absolute, complete, entire, full, perfect, pure, total, ultimate, unalloyed, unmitigated, whole
* Adverbs: absolutely, completely, entirely, fully, perfectly, purely, totally, utterly
Unchangeable, Irreversible
* Adjectives: definitive, final, immutable, inevitable, irrevocable, permanent, unchangeable
* Adverbs: definitive, finally, inevitably, irrevocably, permanently, unchangeably
Extreme, Intense
* Adjectives: absolute, extreme, intense, profound, radical, severe, ultimate
* Adverbs: absolutely, extremely, intensely, profoundly, radically, severely, ultimately
Unqualified, Unconditional
* Adjectives: absolute, categorical, unconditional, unqualified, unreserved, unwavering
* Adverbs: absolutely, categorically, unconditionally, unqualifiedly, unreservedly, unwaveringly
Other Options
* Adjectives: certain, definite, fixed, inherent, intrinsic, inherent, inherent
* Adverbs: certainly, definitely, inherently, intrinsically
Examples
* Absolute silence filled the room.
* Completely exhausted, she collapsed on the sofa.
* Inevitably, the sun will set.
* Unconditionally, she loved her children.
* Ultimately, the truth will come out.
The best choice of adjective or adverb will depend on the specific context and the nuance you wish to convey.