apostate
backslider
blackleg
bolter
collaborationist
collaborator
convert
defector
deserter
fifth columnist
fink
mugwump
proselyte
quisling
rat
recidivist
recreant
renegade
renegado
renegate
reversionist
runagate
scab
schismatic
seceder
secessionist
separatist
tergiversant
tergiversator
traitor
turnabout
turncoat
turntail
worker
strikebreaking