Quotes: Chronic Backstabbing Disorder

Amazingly, Batman does not coldcock the Joker and throw him in jail at that moment. Instead, he grudgingly decides to team up and investigate alongside his deadliest foe... Sure enough, Joker tries to kill him by running him over with a taxi four panels later. To be fair, though, as the Joker says, trying to kill Batman every time you see him is kind of a tough habit to break.
Chris Sims on Batman: The Brave and the Bold #191

Brilliantly, Avon admits that he has known about Blake's whereabouts for some time and had his pact with Zukan worked out he would have left him on Gouda Prime to rot and said nothing. What a cold, devious man he is. He's precisely the sort that you want on your side during a conflict, somebody who is willing to do anything to get the job done and leave his personal feelings at the door. He is exactly the wrong person you want on your side during peace time though, he would stab you in the back sooner than look at you.
Joe Ford on Blakes Seven, "Blake"

"The enemy of my enemy dies next."
— Unattributed

"If nothing, you can always trust that you can't trust Sliske."
Wahisietel, RuneScape

"And here I thought I'd had my quota of betrayal and attempted murder this year...."
Garrus, Mass Effect 2

"He is what they call in the thrillers a double agent, a triple agent in this case, and agent to infinite regression..."
Sol, Hyperion

Niko: That is the plan, Jacob. I will put a bullet in his heart for every life he ruined, for every agreement he went back on, for every friend he betrayed.
Jacob: Dat be a whole heap of teeth, ya know, Niko. I don't tink we have enough ammo fe shoot him dat many times, ya know.
Niko: Perhaps one bullet in his brain will have to do then.
Jacob: Seen.

Elizabeth: Whose side is Jack on?
Will: At the moment?

Drizz'l: Hold it. What do you think you are doing here?
Black Mage: I'd say I was joining the winning team, but that would imply there existed a time where I wasn't on Team Evil.

"If his treachery could ever hurt anyone more than himself, I'd have to stop him."

"Who could be foolish enough to relax his guard with a man who constantly betrays everyone around him?"
Sir Bismarck Waldstein, Code Geass

"Damn, but I'm gonna need a lot of this..."
Revolver Ocelot (in reference to his CBD medication), The Last Days of FOXHOUND,

"So now you're with Konoha? You guys sure keep busy, switching sides all the time!"
Tayuya, Naruto

"I did warn you not to trust me, you know."
Petyr "Littlefinger" Baelish, A Song of Ice and Fire

"Diplomacy is the art of saying 'Nice doggie' until you can find a rock."
Will Rogers

Sheva: I thought they were partners?
Chris: Wesker doesn't give a damn about anybody but himself.

"That thieving lizard Shendu will pay dearly for his betrayal!"
Daolan Wong, Jackie Chan Adventures

"Is it my fault that you are so trusting?"
Mozenrath, Aladdin: The Series

"I know to whom I owe the most loyalty, and I see him in the mirror every day."

"Because that's what Shawn Michaels generally does."
John Cena (asked why he thinks his tag partner is going to backstab him)

"But fortunately I anticipated your anticipation of my anticipation of your anticipation of my anticipation of your anticipation of my treachery!"
Dr. Zarkendorf, Plan 7 of 9 from Outer Space

"What? Naesala and the ravens of Kilvas betrayed us? Again?"

"Treachery keeps the wits sharp."
Megatron, Beast Wars

"Curse your sudden but inevitable betrayal!"
Wash, Firefly

"You want to kill me, don't you, Tucker? Well take a number and get in line."
Eric Qualen, Cliffhanger

"Trust not a man who has betrayed his master, nor take him into your own service, lest he betray you too. I learned the truth of this, to my sorrow, the day we arrived in Azahd as the Sultan's honoured guests."

Gwen: Kevin? Why would you tell this to Argit? He's a con man who would sell his mother for lunch money!
Kevin: I happen to know he got top dollar for his mom.
Ben 10: Alien Force, "Con of Rath"

Sunfire: I have technically never betrayed the X-Men as I hold no loyalty to you people whatsoever.
— The parody fic Apocalypse Anonymous

"What is it that troubles you, then? Surely you are not still dwelling on Discord's betrayal. We knew that he was unreliable. What we did not know was that he was a fool. His betrayal was as inevitable as Tirek's, yet he did not see it coming."
Princess Luna, The Stars Ascendant

I don't think much of blind loyalty, but I think a lot less of blind betrayal.
President Josiah Bartlet, The West Wing