Nouns

(n)poltroon, craven, recreantan abject coward
(n)deserter, apostate, renegade, turncoat, recreant, rattera disloyal person who betrays or deserts their cause or religion or political party or friend etc.

Adjectives

(s)recreant, renegadehaving deserted a cause or principle“some provinces had proved recreant”, “renegade supporters of the usurper”
(s)craven, recreantlacking even the rudiments of courage; abjectly fearful“the craven fellow turned and ran”, “a craven proposal to raise the white flag”, “this recreant knight” (Spenser)