diehard

overenthusiastic person

Synonyms: bitter ender, Bourbon, dyed-in-the-wool, extremist, fanatic, fogy, fundamentalist, intransigent, mossback, old liner, praetorian, pullback, reactionary, right, rightist, right-winger, standpat, standpatter, stick-in-the-mud, Tory, true blue, ultraconservative, zealot