Despite the mediator's best efforts, the opposing sides in the dispute remained intransigent [ɪnˈtræn.sɪ.dʒənt].

intransigent
adj [ɪnˈtræn.sɪ.dʒənt]

Intransigent is a formal word that describes a person who refuses to compromise or abandon an often extreme position or attitude. It can also describe a thing, such as a system or point of view, that shows the same kind of stubbornness.

from the Spanish adjective intransigente, meaning "uncompromising," and ultimately from the Latin verb transigere, "to come to an agreement."

English