Crossword Dictionary

inexorable

adamant, adamantine, inexorable, intransigent - a 
impervious to pleas, persuasion, requests, reason; "he is adamant in his refusal to change his mind"; "Cynthia was inexorable; she would have none of him"- W.Churchill; "an intransigent conservative opposed to every liberal tendency" 

wordplays

synonyms

relentless, unremitting, unstoppable, certain, ineluctable, ineludible, inescapable, inevitable, necessary, sure, unavoidable, unescapable

in a sentence

an inexorable conclusion

the inexorable rise of a political movement

merriam-webster 

etymology 

"unyielding, unrelenting," 1550s, from French inexorable and directly from Latin inexorabilis "that cannot be moved by entreaty, unyielding," from in- "not, opposite of" (see in- (1)) + exorabilis "able to be entreated," from exorare "to prevail upon," from ex"out" (see ex-) + Årare "to pray to, beseech" (see orator). Related: Inexorably; inexorability.

etymonline