The noun ultimatum is one of those words that needs no modifiers.
ultimatum: In diplomacy, the final terms presented by one power (or group of powers) to another, the rejection of which may lead to the severing of diplomatic relations, and eventually to a declaration of war. –OED
For ordinary people (i.e., non-diplomats), the word means
a final condition or stipulation; one’s last word on a matter.
So why do so many writers insist on modifying this strong noun with the adjective “final”?
Burger King gives final ultimatum to Aguilar
Scott issues the Hood a final ultimatum; stop or be shot at.
JEDDAH, November 23: Al-Ahly of Jeddah have officially issued a final ultimatum to manager Argentinian Edgardo Bauza…
After a string of wrists slaps and threats, toxin-lovin’ Babyshambles rocker Pete Doherty has been issued a final ultimatum from a London Judge: “If he does not show the motivation in four weeks, it will be prison…
Either an ultimatum is ultimate or it isn’t. If a woman’s ultimatum to her boyfriend is, “Sober up or lose me,” then she can’t take him back if he fails to sober up. If she does, then she hasn’t issued an ultimatum. At most, she’s made an empty threat.
“Final ultimatum” makes as much sense as “very unique.”