Recreant

(adj)
Cowardly or unfaithful

(noun)
Coward or traitor

Examples:
1. The recreant firefighter was too scared to go inside June’s burning house.
2. June caught her recreant boyfriend at the movies with another girl.

3. The recreant wouldn’t chase after June’s purse snatcher.
4. June’s friend turned out to be a recreant when she gossiped about her behind her back.