KUJAN: Not from me, you piece of s***. There is no immunity from me. You atone with me or the world you live in becomes the hell you fear in the back of your tiny mind. Every criminal I have put in prison, every cop who owes me a favor, every creeping scumbag that works the street for a living, will know the name of Verbal Kint. You'll be the lowest sort of rat, the prince of snitches, the loudest cooing stool pigeon that ever grabbed his ankles for the man. Now you talk to me, or that precious immunity they've seen so fit to grant you won't be worth the paper the contract put out on your life is printed on.
Kujan thinks he can manipulate Verbal through these kinds of scare tactics. But Verbal is way out in front on the manipulation score. The criminals who owe Kujan won't be able to attack Verbal because Verbal is really Söze, and his identifying marks as Verbal—limp, bad arm—are fake.
VERBAL: Where's your head, Agent Kujan? Where do you think the pressure's coming from? Keyser Söze—or whatever you want to call him—he knows where I am right now! He's got the front burner under your ass to let me go so he can scoop me up ten minutes later! Immunity was just a deal with you assholes. I got a whole new problem once I post bail.
KUJAN: So why play into his hands? We can protect you.
VERBAL: Oh, gee, thanks, Dave. Bang-up job so far. Extortion, coercion. You'll pardon me if I ask you to kiss my pucker. The same f***ers that rounded us up and sank us into this mess are gonna bail me out? F*** you. You think you can catch Keyser Söze? You think a guy like that comes this close to getting caught and sticks his head out? If he comes up for anything, it will be to get rid of me. After that...my guess is you'll never hear from him again.
Verbal manipulates Kujan by acting like he's afraid of Söze, when he really is Söze. And, ironically, he has stuck his head out—he's in this office with Kujan. But, once he leaves, Kujan probably won't be able to track him down, as Verbal's last statement strongly suggests.
KUJAN: You had a gun, then why didn't you help him? He was your friend!
VERBAL: Because I was afraid, okay? I was afraid.
KUJAN: Afraid of what?
VERBAL: It was Keyser Söze, Agent Kujan! The Devil himself! How do you shoot the Devil in the back? (Pause, holds up his crippled hand). What if you miss?
Verbal doesn't really have a damaged hand or a limp. This is pure manipulation. He convinces Kujan that he's physically disabled and afraid, when, in reality, he's the very man who killed Keaton and the other criminals.
KUJAN: No, Verbal. You weren't friends. Keaton didn't have friends. He saved you because he wanted it that way. It was his will.
KUJAN: Keaton was Keyser Söze.
Kujan doesn't really believe Keaton was Söze, just that he's the nearest thing—the main criminal manipulating events from behind the scenes. Kujan doesn't believe that the actual Söze, with his masterly criminal abilities, really exists (though he knows better once the movie ends).
KUJAN: He used all of you to get him on that boat. He couldn't get on alone and he had to pull the trigger himself to make sure he got his man. The one man that could identify him.
VERBAL: This is all bulls***.
KUJAN: He left you to stay behind and tell us he was dead. You saw him die, right? Or did you? You had to hide when the first police cars showed up. You heard the shot, just before the fire but you didn't see him die.
When Verbal says, "This is all bulls***," he's actually telling the truth. He's successfully manipulated Kujan into believing a false version of events and mistaking Keaton for the arch-criminal. Verbal pretends to be resistant to Kujan's theory about Keaton, but it's actually the very thing he wants Kujan to believe.
KUJAN: He programmed you to tell us just what he wanted you to. Customs has been investigating him for years. He knew we were close. You said it yourself. Where is the political pressure coming from? Why are you being protected? It's Keaton making sure you tell us what you're supposed to. Immunity is your reward.
In reality, Verbal's being protected because he is a master manipulator pulling the strings of power. He's been protecting himself through his own devious application of his abilities. But Kujan thinks Keaton is still alive, contrary to what Verbal told him.
VERBAL: But why me? Why not Hockney or Fenster or McManus? I'm a cripple. I'm stupid. Why me?
KUJAN: Because you're a cripple, Verbal. Because you're stupid. Because you were weaker than them. Because you couldn't see far enough into him to know the truth.
Verbal is actually super smart, and has successfully convinced Kujan that he's stupid and that he wasn't able to catch on to Keaton. He plays his part like an actor, manipulating Kujan into believing that he (Verbal) was left alive in order to feed the cops a line of nonsense about Keaton being a good guy. (Of course, Keaton probably was a truly bad guy, but still no match for Verbal/Söze as a criminal mastermind.)