Traitor, or far harsher, a Judas.
You may call him a patriot but I prefer the name turncoat, he deserted us and joined the other side.
Traitor, betrayer, backstabber, informer, double-crosser, turncoat...
If my daughter goes to the Cape I might be a turncoat.
The Turncoat - 2013 was released on: USA: 12 February 2013 (internet)
Hong Kong - 1960 The Turncoat - 1.9 was released on: USA: 23 November 1960
The Revolutionary War general was Benedict Arnold, who was labeled a turncoat when he went over to the British side.
The cast of The Turncoat - 2013 includes: Kim Carrell Angie Jepson Marks Georgia Lyman Liam McNeill
Typically a turncoat if they are claiming allegiance or loyalty to you, and are then acting against you with another person.
The cast of The Little Turncoat - 1913 includes: Shorty Hamilton Ann Little as Violet Gordon Harold Lockwood as Captain Gordon