I don't remember if someone has already posted a list like this, but here are some moments that show Leland really cares for Monk:
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Foreign Man: Leland says he's not going to let Monk suffer the same he did when Trudy died and ask him to promisse he wouldn't get so involved in Samuel's case;
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On the Run I: Leland pretended to shoot and kill Monk just to protect him and have enough time to figure out what was behind Monk's prison;
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Gets Fired : Leland tried to make the Commissioner change his mind about taking Monk's detective license forever;
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Mrs. Monk: the "you're the guy" speech, although it was Randy who had listened to it, proved Leland was proud of working with Monk and was trying to get him back to the police. Then, when Monk thought Trudy could be alive, Leland supported him and even felt useless because wanted to help Monk but didn't know how to;
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The Cobra: Leland got desperate when he knew Monk was buried alive, he put every cop to dig and was the one who guessed where Monk was. He saved his life. Again;
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Red Herring: in the Police Department, Leland asked Monk if he had already found a new assistant and added he's been worrying about him;
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Bumps His Head: Leland comforts Natalie and assures her he'll find Monk and when he finally does, he demonstrated being happy to meet Monk again;
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Meets His Dad: Leland convices Monk to give his Dad a second chance;
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Makes a Friend: Leland suspects Hal can be dangerous and confronts him, together with Randy and Natalie. Then, in the end, when they enter Hal's apartment and Hal is up to shoot Monk, he orders Hal to get his hand out of his friend;
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Takes Manhattan: Leland goes to New York with Monk to help him to track on the clues Dale Biderback had given. he investigates why the meeting between Monk and Tennyson Warrickson had been canceled and helps Monk to solve the Embassador case so that Monk can meet Tennyson. In the end, he is beside Monk and grabs his hands when Monk asks to be alone with the guy.
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The Rapper: Leland accepts to go with Monk at the Rapper's mansion in order to give him support to put an end to the contract Monk did;
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Daredevil: Leland immeadiately goes to Monk's appartment as he listens how Monk is. He stays all the time beside him during the "suicide watch", he insists on going with Monk to the bathroom and then suffers together with him on the sofa

. And then, he also gives Monk a lesson about comparing himself to Harold;
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On the Run II: After clearing everything out, Leland orders the cops to let Monk free and hugs him;
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Can't See A Thing: Leland doesn't let Monk give up of working after he gets temporarily blind;
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Really, Really Dead Guy: Leland defends Monk when the FBI guy put him out of the case, saying the guy is wrong about him;
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Gets Cabin Fever: Leland goes with Monk to the FBI Cabin just to protect him, since he doesn't trust "those guys", as he says, even though, that is his birthday;
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The Godfather: Leland tries to convince Monk not to go undercovered into the FBI investigation about the mafia guys. If he doesn't care about Monk or wanted him dead, he would never do that.
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