Tyrion: I heard there was some trouble in Littlefinger's brothel the other night.
Janos Slynt: Mmhmm. Nasty business, had to be done.
Tyrion: Yes, of course. The City Watch must keep the peace. Only, I hadn't realised peace depended on killing babies.
Janos Slynt: Orders are orders.
Tyrion: Quite right. Especially the Queen's orders.
Janos Slynt: I never said they were the Queen's orders.
Tyrion: No, but who else would want to murder King Robert's bastards? She's always been a jealous woman.
Janos Slynt: You know your sister better than I do.
Tyrion: You've heard the awful rumors about my brother and sister.
Janos Slynt: I don't listen to filth.
Tyrion: That's good of you, but you have heard them. I suppose people who do believe that filth consider Robert's bastards to be better claimants to the throne than Cersei's children.
Janos Slynt: Joffrey is my king, the rest doesn't interest me.
Tyrion: I appreciate your loyalty. Tell me, when your men slaughtered Ned Stark's men in the Throne Room, did you give the order?
Janos Slynt: I did, and I would again. The man was a traitor. He tried to buy my loyalty.
Tyrion: The fool. He had no idea you were already bought.
Janos Slynt: Are you drunk!? I'll not have my honor questioned by an imp!
Tyrion: I'm not questioning your honor, Lord Janos. I'm denying its existence.
Janos Slynt: If you think I'll stand here and take this from you, dwarf...
Tyrion: "Dwarf." Hmm, you should've stopped at imp. And yes, you will stand here and take it from me. Unless you'd like to take it from my friend here [motions to Bronn]. I intend to serve as Hand of the King until my father returns from the war, and seeing as you betrayed the last Hand of the King, well I just wouldn't feel safe with you lurking about.
Cripples, Bastards, and Broken Things - S1-E4
Daenerys Targaryen: If you ever lay a hand on me again, it'll be the last time you have hands.
Tyrion Lannister: If the day ever comes when you're tempted to sell me out, remember this: Whatever their price, I'll beat it. I like living.
Davos: Westeros is not the world, Your Grace. We need to look east for ships and men. Ten-thousand skilled soldiers fight for the Golden Company.
Stannis: The Golden Company!?
Davos: They've never broken a contract.
Stannis: They're sell-swords!
Davos: We're willing to use blood magic to put you on the throne, but we're not willing to pay men to fight?
Blackfish: Kingslayer.
Jaime: Blackfish.
Blackfish: I assume you're here to fulfill the vow you gave my niece. I don't see Sansa and Arya.
Jaime: I don't have them.
Blackfish: Pity. Do you wish to resume your captivity? [Jaime shakes his head "no."] Then why are you here?
Jaime: You know why I'm here. This castle belongs to House Frey. You're trespassing. In the name of King Tommen, I order you to surrender, or...
Blackfish: Or you'll kill Edmure. My nephew's marked for death no matter what. Hang him and be done with it.
Jaime: It won't stop with Edmure. You'll force me to storm the castle. Hundreds will die.
Blackfish: Hundreds of mine. Thousands of yours. If you can breach the walls.
Jaime: We'll breach them, and kill every last one of you. But if you surrender, I'll spare the lives of your men, on my honor.
Blackfish: Your "honor." Bargaining with oath-breakers is like building on quicksand.
Jaime: The war is over, Ser. Why sacrifice living men to a lost cause?
Blackfish: As long as I'm standing, the war is not over. This is my home. I was born in this castle, and I'm ready to die in it. So you can either attack, or try to starve us out. We have enough provisions for two years. Do you have two years, Kingslayer?
Jaime: You clearly have no intention of saving your men's lives. Why did you come treat with me?
Blackfish: Sieges are dull, and I wanted to see you in person, get the measure of you.
Jaime: Well now you have.
Blackfish: Aye, now I have. I'm disappointed.
Tyrion: No-one is very happy, which means it's a good compromise, I suppose.
Cersei Lannister: When you play the game of thrones you win or you die. There is no middle ground.
Tyrion Lannister: The Eyrie. They say it's impregnable.
Bronn: Give me 10 good men and some climbing spikes... I'll impregnate the bitch.
Arya Stark: They said you found the bastard and the wolves are fighting the lions and the savage... Something about the savage.
Ned Stark: Where did you hear this?
Arya Stark: In the dungeons, near the dragon skulls.
Ned Stark: What were you doing in the dungeons?
Arya Stark: Chasing a cat.
Robb Stark: Good. Next time I see you, you'll be all in black.
Jon Snow: It was always my color.
Tyrion Lannister: Speaking for the grotesques, I'd have to disagree. Death is so final, whereas life... Life is full of possibilities.
Eddard Stark: Winter is coming.
Tyrion Lannister: A Lannister always pays his debts.
Brother Ray: Violence is a disease. You don't cure a disease by spreading it to more people.
Answer: Basically it's because he broke his vow. A member of the Kingsguard is sworn to protect the king at all costs. Jaime elaborates more on the deed to both Catelyn Stark and Brienne of Tarth, telling Catelyn that no matter what course of action he took, he would be breaking one vow or another (i.e. if he obeyed the king, he would conversely be disobeying his own father), and telling Brienne that the Mad King was planning on burning all of King's Landing, but he did not bother to tell Ned Stark that. Ned Stark felt that killing Aerys was dishonorable and excessive. Robert Baratheon still could have usurped the throne without Aerys being killed.
Phaneron ★