PLUCKIEST
PLUCKY
gutsy, plucky
(adjective) marked by courage and determination in the face of difficulties or danger; robust and uninhibited; “you have to admire her; it was a gutsy thing to do”; “the gutsy...intensity of her musical involvement”-Judith Crist; “a gutsy red wine”
feisty, plucky, spunky
(adjective) showing courage; “the champion is faced with a feisty challenger”
Source: WordNet® 3.1
Adjective
pluckiest
superlative form of plucky: most plucky
Source: Wiktionary
PLUCKY
Pluck"y, a. [Compar. Pluckier; superl. Pluckiest.]
Definition: Having pluck or courage; characterized by pluck; displaying
pluck; courageous; spirited; as, a plucky race.
If you're plucky, and not over subject to fright. Barham.
Source: Webster’s Unabridged Dictionary 1913 Edition