absolutist

Short definition from Wiktionary

Noun

1. 1
   One who is in favor of an absolute or autocratic government.
2. 2
   One who believes that it is possible to realize a cognition or concept of the Absolute.
3. 3
   An uncompromising person; one who maintains certain principles to be absolute.

Adjective

1. 1
   Of or pertaining to absolutism; arbitrary; despotic; uncompromising.