9. "The Therapists" (Season 6, Episode 9)
Catchphrase: "Somebody gotta get fucked up, Larry."
Despite his rampant narcissim, LD truly cares for Cheryl. That much is clear because we've never seen him so vulnerable and susceptible to another person's advice as he is here with his therapist (Steve Coogan). Cheryl is following her own therapist's advice even more religiously, so to subvert her and win Cheryl back, Larry, Jeff, and Leon conspire to create a scenario where Cheryl's therapist will feel impressed by Larry and inclined to send Cheryl back to him.
Naturally, things backfire. Larry's doctor pulls off a faux mugging but is arrested in the process, and Cheryl's therapist falls for Larry and thusly tries to effectively end the David marriage. In the end for all his scheming, Larry is even farther away from ever winning Cheryl back than the episode's beginning.