A Stock Phrase wherein a character acknowledges a past missed opportunity just as they are about to do what they were unable to (or chose not to) all those years ago. Often, the character spared a foe's life in the past and has since come to regret letting the Ungrateful Bastard live, in which case the phrase usually comes during a Sword over Head moment and may be accompanied by Prepare to Die. Bonus points if the character in question is a villain who foolishly killed one of his enemies in the Back Story but left their child, now The Hero, alive out of scorn, or a Mentor who couldn't bring himself to kill his beloved pupil, now the Big Bad, even when their Omnicidal Maniac tendencies became apparent.
Note that the phrase may be used in regards to plenty of things other than murder: a risk not taken, a path not followed, a highschool sweetheart not smooched - any of these may provoke the phrase years later, optionally accompanied by a wistful expression and/or a tear in the eye.
This trope can also appear in more disguised forms, without having to invoke the Stock Phrase. "I have a certain phone call to make"/"there's a family waiting for me"/"I just realised I need to visit an old friend"/etc. are all stock sentences that stem directly from this concept.
Loosely related to I Always Wanted to Say That.
- Calvin and Hobbes: Calvin's dad uses the "Should have thought of this years ago" variation in one bedtime story strip: the story is about a disembodied hand that goes around strangling people and was never found, so to this day it could be anywheOHMIGOD IT'S GOT ME!!!! With Calvin out cold, his dad says the above line.
- Dirty Sympathy Klavier jokingly apologizes to Apollo for not pushing his brother off the Swiss Alp when he was nine.
- Antz: When Col. Cutter finally rebels against Gen. Mandible's evil ways and tries to help the ants the general tried to drown.
General Mandible: Cutter, what are you doing?Colonel Cutter: Something I should have done, a long time ago. [extends his hand to the worker ants] This is for the good of the colony, sir.
- The Kung Fu Panda films both have the phrase, in which Mr. Ping the goose told his son Po the panda something he should've told him a long time ago. First Film: His secret ingredient soup. Second Film: His adoption.
- In Disney's The Hunchback of Notre Dame: At the climax, Frollo finally reveals to Quasimodo that he killed his mother who was trying to save him (rather than abandoning him like Frollo had always told him). Frollo then delivers the famous line, "And now, I'm going to do what I should have done... TWENTY YEARS AGO!" and proceeds to throw poor Quasi off the cathedral balcony. Too bad he ended up dying instead of killing Quasi.
- Moana: After Moana finds some old ships hidden in a cave discovers that her people were once voyagers, her father sets off to burn said ships like he said he should have done long ago. He doesn't get very far though, because he gets told he has something else to worry about.
- Bridget Jones' Diary
Mark Darcy: I should have done this years ago.Daniel Cleaver: Done what?Mark Darcy: This. [Punches Cleaver, hard]
- A Cinderella Story
Sam: Austin? What are you doing?Austin: Something I should have done a long time ago. [he kisses her]
- Call of the Prairie (1936)
Johnny Nelson: I'm going to do what I should have done a long time ago...I'm going to round up those crooks!
- A History of Violence:
Tom: I should've killed you back in Philly.Carl: Yeah Joey... you should have.
- Passport To Paris
Jeremy: I quit. [snip various protests] No, no. I need to thank you. For giving me the courage to do what I should have done a long time ago.
- Downfall has Hitler say something similar to his entry on the Real Life section in his famous Villainous Breakdown scene.
Hitler: For years the military has hindered my plans! They've put every kind of obstacle in my way! What I should have done is liquidate all the high-ranking officers, like Stalin did!
- The Buffy the Vampire Slayer episode "Seeing Red" has a perfect example after Spike's Attempted Rape of Buffy.
Buffy: Ask me again why I could never love you!
Spike: Buffy... My God, I didn't--
Buffy: Because I stopped you! [quieter] Something I should have done a long time ago.
- The Doctor Who episode "Father's Day"
The Doctor: Jackie Tyler, do as I say! GO! AND CHECK! THE DOORS! [she does] Should've done that ages back.
- Star Trek: Enterprise episode "These Are the Voyages..."
Riker: I think I'm ready to talk to Captain Picard. Should have done it a long time ago.
- Greg the Bunny
Gil: Hey there son!Jimmy: What're you doing here?Gil: Something I should have done a long time ago! [wraps his arms around Jimmy and gives him a big hug].Jimmy: What? Molest me?
- Power Rangers Time Force episode "The End of Time: Part 3"
Jen: I should have told you this a long time ago. I love you!
- Star Trek: The Next Generation, final episode: Picard joins the bridge officers' poker game at the end, and is offered to deal. He says this line, to which Troi says 'You were always welcome.'
- Battlestar Galactica: Colonel Tigh in "Revelations".
"I should have told you when I first found out, but I didn't have the guts."
- The Mrs Hawking series: In part V: Mrs. Frost, somewhat ironically, when Nathaniel says that if he knew it would win him Mrs. Hawking's affection, he would have let "some brute beat the stuffing out of me" ages ago.
- Ratchet: Deadlocked
Gleeman Vox: Now I'm going to do what I should have done a long time ago... I'm going to give DreadZone fans the finale they always wanted... It's a little one act play I like to call... Death... of A Lombax.
- In Mass Effect 2, you have a second encounter with the annoying reporter you met in the first game. If you didn't punch her then and do the second time, you say "I should have done that the first time we met."
- At the end of Merill's Rivalry path in Dragon Age II, she says this before smashing the Eluvian.
- At the end of Mega Man 7, Mega Man is sick of fighting Dr. Wily over and over again only for him to escape and try again to take over the world, so he delivers this line and starts charging his Arm Cannon. However, he's stopped by a Three Laws-Compliant and Bass rescues Wily.
- In Resident Evil 5, Albert Wesker admits that he should have killed Chris years ago after the latter ruins his latest and greatest scheme.
- Sly Cooper and the Thievius Raccoonus
- One of the Heavy's revenge lines in Team Fortress 2.
Heavy: I should have done this long ago!
- The Big Bad of Time Crisis 3, Giorgio Zott, pulls this when he gets ready to launch the tactical missiles meant for Lukano.
Zott: I should have gotten rid of that pesky country long ago...
- Family Guy
Lois Griffin: Wha? What are you doing with a gun?
Stewie Griffin: Something I should have done a very long time ago! [shoots Lois]
- Lampshaded by The Simpsons. Marge writes a novel with the main cast as expies of herself, Homer and Flanders. Events play out in a way which mirrors the novel, resulting in Homer confronting Flanders on a cliff (in the book, the expies fall off a cliff in a fight over expy Marge). Homer cites the phrase. He asks Flanders how to be a good husband.
- Episode "Homer Goes to College"
Bart: Well, Pop, what are you gonna do?
Homer: Something I should have done a long time ago! [long pause]
Marge: You don't know, do you?
Homer: No, ma'am.
- Episode "Treehouse of Horror VIII"
[Homer pulls up an axe]
Marge: Homer, what are you doing?
Homer: Something I should have done a long time ago. [turns on Bart with his axe] I'll teach you to mess with my machine!
Bart: [begins screaming and running while Homer chases him]
Homer: I'm gonna chop you good!
- Episode "Homer Goes to College"
- SpongeBob SquarePants:
Squidward: Now now. Calm down. I've should've given this to you a long time ago!
- Parodied in "Jellyfish Hunter". When SpongeBob is in Mr. Krabs' jelly processing plant, he picks up a wrench, and when asked what he is doing, he says, "Something that should have been done a long time ago!"... and then proceeds to fix a loose nut.
- In "Restraining SpongeBob", Squidward says this to SpongeBob while filing a restraining order against him after his usual stupidity gets him injured.
- Gargamel's comment on the use of his Daredevil Dust to capture the Smurfs in The Smurfs episode "Reckless Smurfs".
- Wendy's comment to do something about Photoshop in the South Park episode "The Hobbit"
- Napoleon Bonaparte said "I should have shot him" about Charles Maurice de Talleyrand-Périgord, the Prime Minister of France. Given Talleyrand's record, he probably should have.
- As everything fell apart in 1945, Adolf Hitler said he should have purged the Wehrmacht high command like Stalin did with his 1937-38 purges.