Let Me At Him

A Crime-Time Soap and Detective Drama trope.

A detective (rarely a great one, though), angered by a possible or actual perp being smug, lunges for them and has to be restrained by fellow officers. Not usually part of Good Cop, Bad Cop, more sheer hatred on the part of the detective (often when It's Personal). Particularly vulnerable to stuff like If You Kill Him You Will Be Just Like Him when there is actual murderous intent (this is quite rare in police show, though).

Examples of Let Me At Him include:

Akito gets held back twice when trying to attack Tohru and Kana in Fruits Basket.
The movie Se7en.
Parodied in There's Something About Mary.
Played straight in Mad Max when one of the bikers is let go on a "No Contest" plea.
Lethal Weapon, where they let Riggs fight with Mr. Joshua at the end.
Dirty Harry, although it is more of a statement than done in anger.
Elliot Stabler of Law and Order Special Victims Unit has had trouble controlling himself before.
- Somewhat averted in Law & Order: Criminal Intent: in Season 6, Det. Goren is interviewing convicted serial killer Mark Ford Brady in an effort to find more of his victims before he is executed, and when it becomes clear that Brady raped Goren's mother and may well be his own father, Goren snaps and goes for his throat. There's a prison guard right there in the room, but he doesn't interfere in any way; Goren just gets control of himself.
Happened in an episode of Criminal Minds but it was not one of the team who went across the table at the unsub; it was in fact the priest of the local church, who had helped organize a search for a missing woman in the community, and had been asked to talk to the suspect after they captured him as he was a parishioner and might talk to the priest. The priest—who has remained calm and composed the entire episode—finally loses it when the suspect reveals he chopped up the woman and made her into a stew that he then fed to the search parties.
- Subverted by the episode "Masterpiece", where it's after Rossi's Crowning Moment of Awesome that Jason Alexander's UnSub lunges across the table at Rossi - who promptly gains the upper hand, slams his head against a plate-glass window a couple times, and then calmly lets him go.
Sgt. Kelloway from the movie version of The Mask. Granted, it had definitely become personal at that point, what with them finding a picture of Kelloway's wife in Stanley's pants.
Deconstructed in an episode of CSI where the murderer was a cop who ended up accidentally killing an innocent eighteen year old teenage suspect in interrogation who wouldn't confess by not so accidentally knocking him over onto the concrete floor and let him die of head trauma.
Similar to the Criminal Intent example above, Mulder faces a serial child murderer who claims Mulder's sister as a victim. Driver over the edge, Mulder smacks him out of the seat. When the perp yells, "He hit me!" the guard shrugs and says, "I didn't see it."
Parodied in an episode of The Last Detective, where the protagonist, who is as far from being a Rabid Cop as is possible does this against a criminal who beat up his best friend. It's a rather ineffectual lunge and Dangerous' boss, an Old-Fashioned Copper, finds it amusing.
When Honor Harrington learns, in The Honor of the Queen, that a P.O.W. prison guard has been ordering prisoners raped and beaten, she goes after him with murderous intent. Only the intervention of one of her subordinates, who shoves her arm aside as she's pulling the trigger, keeps her from killing him. Rather than an If You Kill Him You Will Be Just Like Him speech, though, she's told that there's no need to commit career suicide by killing him without a trial, when there's plenty of evidence to convict him and hang him after a full court-martial.
Inverted, subverted, and played straight to different degrees in J.D. Robb's In Death series. Most of the time Eve, the Bad Cop in almost every interview, intentionally provokes this reaction, sometimes even letting them land a blow to justify Kicking Ass and Taking Names. At the same time, some of the series's Complete Monsters and even their Sympathetic Murderers will elicit this reaction from Hot-Blooded cops if it's personal. Sometimes it looks like one party or the other will snap and lunge... only to cool down and call a lawyer or point out a flaw in the suspect's story.
In L.A. Confidential, Bud White's Berserk Button is triggered as he listens to a black suspect confessing to the incidental crime of kidnapping and raping a Mexican woman. He shatters the back of the chair he is leaning on, storms into the interrogation room, violently pushes the suspect against the wall, and places the barrel of his gun into his mouth. Go 50's!
From Scooby Doo, the abomination whose name we shall not speak.
In The Lion King 2, Timon tells Pumbaa to hold him back, and Pumbaa does so. He then yells "Let me at him, let me at him!" and Pumbaa does so.

Pumbaa, I think you're missing the vital point here.

Sgt Bilko featured a similar exchange in a variation of this trope where Bilko ordered his men to hold him back in a serious and threatening tone, then proceeded to struggle against them trying to get at the guy who pissed him off. As he starts to break free, he urges them with greater and greater urgency to hold him back better (so he doesn't have to actually fight).
My Little Pony Friendship Is Magic: When Rainbow Dash is ready to charge headfirst into a problem, Applejack's normally the one who holds her back by her tail, prompting this reaction.
One of the methods of dealing with bullies that Drillbit Taylor teaches the boys is the Holdback Technique, which is faking this trope to make the other party think you want to fight, ideally making them back off. When the boys try it at school, the one being held back is punched. Drillbit is surprised they actually tried it.
In "Homicide: A Year On The Killing Streets," one of the detectives, having brought in a suspect who raped and beat to death his toddler stepson, contemplates giving him a serious station-house beating with the knowledge that no one in the building would blame or implicate him in any way. He doesn't do it, but not out of compassion: he realizes that, tomorrow, somebody just as bad or worse will be in the same interview room and in the end it doesn't accomplish anything. He convinces another detective to conduct the interview instead while he regains his composure.
Almost every time Spinelli tries starting a fight in Recess
An Exbrayat story has this: the inspector in in the interrogation room with the smug little drug dealer, along with a huge, middle-aged cop whose only daughter died of an overdose. When the dealer starts taunting the inspector, he starts to look as though he's going to punch the smartass... only to turn around and deck the other cop in the face. As both stare dumbfounded, he delivers this awesome line: "You disappoint me, Gunther. A two-bit drug dealer lays a hand on you and you just sit there?" Understanding dawns in the cop's face eyes just before fear does in the dealer's. Later we're told that the official version was that the cop saved the inspector from a violent criminal.
Danny on CSI: NY after Aiden's death. He's wanting very badly to rough up the guy he thinks did it, but Mac is admant he can't because it has to go by the book. It was someone else who killed her anyway in the end.
- There was also one that initially appeared similar to the CSI example above, but it turned into a subversion. Flack has the misfortune for a kid to die in custody, during interrogation. It appears he might have gotten overzealous with the kid, but it later turns out the death was drug induced.