an abject coward
a disloyal person who betrays or deserts his cause or religion or political party or friend etc.
having deserted a cause or principle; "some provinces had proved recreant"; "renegade supporters of the usurper"
lacking 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