Team Rocket almost always falls victim to this (they're Team Rocket, after all). For instance, they planned to steal a (then) full set of four Eevee evolutions, each one individually extremely valuable. They get three of them and a huge lead, easily enough to escape — but Musashi/Jesse insists on going back for the fourth one, resulting in their capture. Usually it's because they'll try and steal Pikachu even if they already have a chance to get away with some rare/valuable Pokémon/object.
James openly averts this trope in one episode where he participated in an "orienteering race" in the episode Off the Unbeaten Path. Basically, he competed fairly with his Mime Jr. despite Jessie urging him to cheat like she was doing. In the end, James wins the contest and Jessie gets "blasted off."
The entire Team averted this in an episode where one of their evil plots begins with hawking cheap merchandise at a Pokémon tournament. They make so much money doing this, they decide to call off the rest of the plan and go home winners. Of course, by the time they opened up an even bigger shop, the tournament was over and they were out of money. Back to a life of crime.
There was also the Balloon Race episode where Team Rocket was actually winning the race fair and square before Jesse and James screwed them up by cheating over Meowth's vigorous objections.
Danzo from Naruto tries to hypnotize Mifune so the Kages will elect him leader of their alliance. It doesn't work. Mifune then informs him that he was going to nominate him, but no longer intends to do so, and Danzo attempts to justify his action by claiming that he had to be certain.
Mazinger Z: In one of the Gosaku Ota manga chapters, Dr. Hell plots the next scheme: overwhelm Mazinger-Z with a Macross Missile Massacre as another of his Mechanical Beasts -Deathcross V9- attacks him, and as the Humongous Mecha is weakened and disoriented by the constant battering of missiles and the onslaught of the Beast, shooting a freaking huge missile to finish him off. It was a good plan. It could have even worked... Should Baron Ashura and Count Brocken have worked together. However, they were so eager and impatient for upstaging each other they attacked separately. Brocken shot the big missile without waiting for Ashura — wasting it and forcing them to rebuild the strategy —, and Ashura decided he could use that chance to defeat Mazinger-Z using the Mechanical Beast (because that tactic had worked so well in the past, right?) and humilliating Brocken.
Alice from Girls Und Panzer during a match between her team, Saunders, and Oarai Academy. Her team has numerical superiority (they outnumber the other team two to one), superior weapons and equipment and experienced tank crews compared to Oarai's new, inexperienced team and tanks rescued from the scrap heap. Despite this she still feels to need to listen in on the other team's radio communications which technically isn't cheating, but it certainly isn't cricket either. This comes back to bite her in the ass when the other team, and her own team captain, realize what she is doing.
One French comic named L'élčve Ducobu follows an utterly lazy student who constantly attempts to steal and copy the answers of a Child Prodigy during exams. It doesn't work out too well. When said Child Prodigy tells him that she would gladly actually pass her the answers to copy if he asked her politely, he (hesitantly) does so and she does give him the answers, only for him to immediately give them back to her dramatically, stating that he can't do it like this. He then immediately resumes his schemes.
Films — Live-Action
In Rat Race, while everybody is doing everything they can to keep moving, the Cody Brothers stop to actively cheat more than any of the others. First of all they decide that since they can't get a plane flight, they'll sabotage an airport (it worked, but they needed a new car). Next they pause to steal another competitor's car engine. And most of all, when they decide to split up for a better chance to win, they end up in a cross-country chase starting with a hot-air-balloon and ending with their car crashing into a lake.
Trip from Herbie Fully Loaded felt compelled to ram Herbie into the wall even though he was in the lead, causing him to crash spectacularly and allowing Herbie to win the race.
Also inverted in the final scene, where the hero stops his car a few yards from the finish line to snog Natalie Wood's character. This actually allows Fate to win, but he refuses to accept victory on those terms and immediately challenges the Great Leslie to another race.
In One Crazy Summer, despite Teddy's protests that he can win the sailing race fairly, his bullying father insists on cheating and even goes so far as to say it's "the only way to win." Naturally, this time they don't.
In Monte Carlo or Bust this happens several times to Sir Cuthbert Ware-Armitage; in fact, after accidentally blowing up his own car, Perkins picks him up on this.
A Running Gag in the Austin Powers films is how Number Two's front companies are making tons of money legally, causing him lots of frustration when Dr. Evil doesn't care and still wants to take over the world, just because.
Number Two: Virtucon alone makes over nine billion dollars a year.
In the Disney Channel Original Movie Brink!, the titular character's rival is actually quite a skilled skater as leader of the X-Blades, but his animosity towards the main character ends up getting him exposed as a cheater.
The Big Match at the end of Unseen Academicals. Since most of Ankh-Morpork United are professional footballers, it's quite likely they could have beaten UU fair and square, but attempting to do so never even occurs to Andy Shank, whose fouling of opposition players ensures that Trev Likely is on the field, and by judicious application of the rules becomes unstoppable.
In Deltora Quest, Reece wants to execute Lief. But to make it look fair, he put him through a trial showing the life and death cards he put into a cup. However he secretly switched the life card with a second death card before doing so. This however backfired when Lief drew a card, faked his clumsiness and dropped it into the fire then saying they could easily tell which card he drew by checking the cup for which on is still inside.
One episode of MacGyver involved a stock car race between the title character and an old rival. The rival had nitrous oxide installed in his car without his permission ("That's illegal"), but even though he was already ahead of MacGyver and would have won had he just kept the course, he decides to use the nitrous oxide he criticized anyway and ends up spinning out on the shoulder.
In the Stargate SG-1 episode "Space Race", the villainous human supremacists sabotage every other vehicle in the race so their favorite will win. In doing so, they take out most of the legitimate competition for Sam and her partner, and convince another enemy pilot to disable the favorite's ship out of spite. Not to mention that the favorite's one true threat managed to overcome the sabotage and probably would have beaten him fairly anyway.
In "Earthbound", an episode of Space 1999, a passing ship on its way to Earth offers to take one human along with them (there is only one free cryogenic capsule). The computer is asked to choose who goes. While the program is running, an obnoxious bureaucrat is busy nagging Koenig about how important he is and so on. He finally stows away on the alien ship but it doesn't end well. So who did the computer eventually choose? The obnoxious bureaucrat!
Lazy Town's Robbie Rotten, whose goal is to return the town to its original lazy state, is the most active person in the town due to his schemes.
This ended up being the undoing of the Korilla BBQ team on season two of Food Network's "The Great Food Truck Race". Fearing elimination they added $2700 of their own money to their cash box to make it look like they sold more than they actually did. They ended up getting caught and disqualified. Ironically enough the team actually made enough money legitimately to earn third place that week and wouldn't have been eliminated had they not resorted to cheating.
Meet Boris Onischenko, Soviet fencer and pentathlete. At the 1976 Summer Olympics, the British team caught him using an epee rigged to score points at the press of a button. While it was being checked out, Boris won eight of his nine matches with a regular epee but was disqualified once the examination was completed.
Taking inspiration from the example above, Cracked.com refers to this trope (specifically in reference to Mr. Onischenko) as the New England Patriots school of cheating — cheat For the Evulz, even if you'd win anyway. Just because.
To expand on what was mentioned in the previous example: in 2007, the New England Patriots were caught illegally taping the hand signals of their Week 1 opponent New York Jets. Coach Bill Belichick was fined $500,000, and the team ended up forfeiting their first-round draft pick. The unnecessary part of this comes when you note that this team was the first team to go undefeated in a 16-game regular season and ended the season with 589 points scored and a +315 point differential (difference between points the team scored and points the team allowed over the course of the season), while their quarterback Tom Brady threw 50 touchdown passes and wide receiver Randy Moss had 23 touchdown receptions, all NFL records. On the other hand, they lost the Super Bowl to the New York Giants.
The Renault Formula One team hadn't won for nearly two years when two senior team members conspired with driver Nelson Piquet Jr. to deliberately crash during the 2008 Singapore Grand Prix to assist teammate Fernando Alonso to win the race. When the truth emerged in 2009 there was a huge uproar, the plotters were banned from racing, sponsors pulled out early and Renault's brand image was tarnished. Funny thing is that Alonso and Renault won the next race in 2008 (in Japan) entirely fair and square.
The same team's forerunner, Benetton, tried their best to cheat despite them and Michael Schumacher being the best car/driver combination in 1994 after Ayrton Senna died. The Benetton was found to have illegal traction control software hidden in its computer. The team's left out a filter in their refueling rig to speed up pit stops. Schumacher overtook Damon Hill on the formation lap at the British Grand Prix (when rules state no-overtaking), then ignored the penalty and was disqualified from the race and excluded from two more. In the end Schumacher won by one point over Hill after their controversial collision in Australia.
Perhaps the most literal F1 example ever happened in the 2006 Monaco GP qualifying. Simply put, Michael Schumacher stopped to cheat (yeah, him again). After setting fastest lap in qualifying, he parked his car against the wall running wide in the Rascasse corner and stalled his engine, which spoiled rival Alonso's faster flying lap. Schumacher alleged it was an accident. Needless to add, it didn't fly. Cue Schumacher starting from the back of the grid.
Where he finished fifth. Of course had he not stopped in qualifying his speed in the race was such that he could still have won or at least finished on the podium.
After clinching pole on the 2012 Spanish Grand Prix qualifying, the Mc Laren team forced Lewis Hamilton to stop on his in-lap because he hadn't enough fuel to get back to the pits AND produce the minimum 1-litre fuel sample to the FIA. Unfortunately the team said it was "force majeure" (act of God) rather than human error to the stewards. Didn't cut the mustard and he was slung out to the back of the grid as punishment. The same thing happened to Lewis in Canada 2010 which he got away with but since then the rules changed so mistakes like that don't happen again.
Jimmie Johnson has hands-down the best car in NASCAR, especially since it's financed by Rick Hendrick and Jeff Gordon. So why crew chief Chad Knaus was caught illegally altering the car prior to the 2006 Daytona 500 is anyone's guess. Knaus was suspended, the car was impounded, Johnson had to start the race from the rear of the field in a backup car — and he won the race anyway.
Andrew Golota. A Heavyweight boxer who was twice ahead of former world champion Riddick Bowe on points proceeded to low blow him until disqualification. Both times.
In every group playing Diplomacy, there's one guy who, upon hearing that you can backstab people, believes that the whole game is about backstabbing people. So, he does so for some very short term gains, derailing everybody else's carefully laid plans, sending the victim on a long Humiliation Conga as he loses all of his states, and screwing himself over since nobody will deal with him, effectively making victory impossible.
In Blood Bowl, delaying your touchdown to tackle or foul opposing players can be a good way of improving your team's long term position, but also risks your own player being knocked down or sent off, either of which ends your turn and lets your opponent regain the initiative.
F-Zero: This can actually happen to the player: attack your opponents in the wrong place and you might send yourself flying off the track. X and GX actually encourages such behavior by not only giving you an extra life if you smash five people off the track, but placing a huge RIVAL sign above the opponent who is highest on the leaderboard. Should that racer suffer an unfortunate "accident", the sign moves to the highest remaining opponent... Even then, it's still played straight if you're going on the offense: Attacking costs you speed — a LOT of it (especially the Spin Attack), and even on Master difficulty the best way to win, is simply to stay on the course, and use as much boost as physically possible whenever you can — not wasting speed to attack... not that killing your RIVAL doesn't help.
Knights of the Old Republic has a few such incidents, but the most obvious is the Mandalorian genocide of the Cathar over little more than bad blood from the Exar Kun rising or before. They get away with it for quite some time, but when their responsibility was confirmed by the Revanchists, the entire things blew up in their faces. Not only did they fail to completely exterminate the Cathar and they gave the Republic's denizens yet more reason to rally to the banner, but this proved to be such a PR explosion for Revan and his followers that the Jedi Council — which had previously been on the verge of trying to forcibly disband them — stayed its hand and allowed the Revanchists to join the fray with little more than a stern word, thus paving the way for Revan's tactics and the addition of his Jedi followers to turn the tide.
Resident Evil 4 has this trope as its motivation for eighty percent of the game. At the end of Chapter 2-1, Leon has rescued Ashley and signaled for the rescue chopper, when Saddler appears and starts monologuing about his big plan, which is already complete - inject Ashley with Las Plagas and have her under Saddler's control when she gets home. He then notes that Leon can't stop him, since he was injected as well while unconscious. But then, despite the fact that Saddler literally has to do nothing to win, his toadies show up and shoot flaming crossbow darts at them. Then they shoot down the chopper as well and proceed to try and kill Leon and Ashley for the rest of the game. Why? Because, as Saddler states just after rattling off his entire plan, he wants to squeeze the US for some ransom money before sending her back. Had he simply not given in to simple greed, he would have won.
A frequent strategy used when playing against the computer in Grand Prix mode of a racing game like the original Super Mario Kart was to hang back a bit near the end to sabotage the leading AI opponent so that the player would gain a greater point advantage. Much like the Need for Speed example, this is actually much better with two players, at least before the latest version specifically disallowed this strategy. One player hugs the turns and goes for speed, while the other plays demolition derby, hangs back in third or fourth place, where they get the good weapons, and mows down the competition for the speed player.
In Tropico, the player (El Presidente) has the option of rigging elections which moves about 10% of the votes to your favor. You can do this even if you are going to win the election in a landslide, although this will upset your people.
The introduction of Wacky Races: Crash & Dash showed Dick Dastardly zooming past all of the other racers without any trickery whatsoever - only for him and Muttley to stop so they could try to blow up a bridge.
The Trope Namer, Dick Dastardly from Wacky Races, frequently stopped to cheat even though he was way out in the lead, allowing his opponents to catch up and overtake him. More than one person has suggested he's doing this on purpose, for varying reasons. These failed schemes always put him in last place, but every time he'd be back in first to try again. This would repeat 3-5 times an episode. Think about it for a minute; he could go from dead-last with a damaged vehicle to a commanding lead several times a race. The Mean Machine had to be far and away the best vehicle in the race, and he'd piss that away because he's the baddie and has to cheat. And the only race in which he won, Dastardly gets disqualified due to a last-second cheat.
It actually makes a lot of sense that the Mean Machine is far superior to the other racecars, given that it's a rocket-propelled vehicle going up against (among other things), a Depression-era coupe, a World War I-era fighter that can barely fly, a glorified go-kart powered by a steam boiler in an advanced state of disrepair, and what seems to be a weird amalgam of a surplus army tank and a street sweeper. Really, to look at them, the only vehicles that should have even the faintest hope against the MM are Peter Perfect's Turbo Terrific (which is actually, you know, a RACE CAR), and arguably, Pat Pending's Convert-a-Car, if only due to the plethora of resources it has (that it can turn into an ACTUAL rocket, among other things, doesn't hurt either).
Issue #4 of the Gold Key comic book (Aug. 1971) has all the racers employing a book entitled How to Win a Race by Hook or Crook, written by Dastardly himself. Penelope Pitstop would effectively eliminate Peter Perfect and Red Max by getting them to fight over her.
The Wacky Races Forever pilot lampshaded the hell out of this by having a scene where Dick Dastardly is taking a nap waiting for the other racers, wakes up, declares his intent to cheat, and when pointed out he's within three feet of the finish line, proudly declares he's a villain and therefore has to cheat.
Issue #13 of the Laff-a-Lympics comic book (Marvel, Mar. 1979) shows that Really Rottens team co-captain Dread Baron is Dick Dastardly's brother.
Arguably, the most blatant evidence they care more about cheating than winning is the episode where the first half was in desert and the second in Scotland. After three of the four events, the Rottens were leading with 95 points while the other teams had 40 points each. Then the last event started: a three-legged kilt race. (A three-legged race where the racers wear kilts) The Rottens race on a threadmill attached to a car driven by Dread Baron, who produced a rulebook stating that, for as long as they run in three-leg style, that wasn't cheating. Also, Dirty and Dastardly Dalton disguised themselves as Snagglepuss and created a fake Finish Line to delay the Yogi Yahooeys. In the end, the Rottens lose 25 points for using the threadmill, 25 points for forging the rulebook that made the use of the threadmill seem legal, and 25 points for delaying the Yogis. (Who got 5 points of bonus in reparation, allowing them to beat the Scoobies for the gold medal)
Spike, the bulldog who opposed Tex Avery's Droopy in various competitions, was practically built on this concept. The biggest evidence of this was the episode "Mutts About Racing", that featured Droopy and Spike as rival race car drivers. One would think Spike and Dick were driving school buddies or something like that.
This is parodied in the episode of South Park, "Asspen", where Stan gets stuck in a crappy 1980s-style "win-the-race-to-save-the-old-rec-center" plot. In the final climactic race between Stan and the annoying jerk, the jerk takes a ridiculous amount of time sabotaging the course to keep Stan from winning. Of course, the jerk is an excellent skier, while Stan can barely ski faster than a crawl. He's so slow that the obstacles don't slow him down any further. He just climbs over them. Ultimately the villain is defeated by matters unrelated to the race anyway.
In COPS, Classy Cat Burglar Nightshade enters a beauty contest to get at the "fabulous prizes" offered (and to rub it in the face of the C.O.P.S. that she hadn't done anything wrong). Naturally, she can't resist making off with the entire prize hoard. Equally naturally, once she's caught, she's informed that if she'd held off for five minutes, she would've won legitimately.
In an episode of Johnny Test, during a race, a pair of villains stop to cheat (or plan to) twice while they're already in the lead. One of the two tries to tell the other that they're already winning. The other one says that his plan is going to make sure they stay in the lead.
Constantly employed by the Vanguard of Justice in the Heavy Gear CGI TV series.
A Cow and Chicken episode featured Cow and Chicken's snail cousin, who entered a relay race because it was the only way Chicken's team would not be disqualified for not having enough members. Being a snail, he was quite slow but his opponent insisted on stopping to cheat despite the fact they could have easily won. (Even Chicken pointed it out to the cheaters. Snail crossed the finish line first and then revealed to have a normal set of legs and started running. He later admitted he didn't think about doing it during the race.
Done in Thundarr The Barbarian, well except that there wasn't really any cheating in a race that explicitly had no rules. Nonetheless, everyone else in the race took a commanding lead in their wizard-provided vehicles and robots, and only lost because they decided to hang back and kill their competition instead of, you know, just winning.
Lippy the Lion and Hardy Har Har once applied for a job as truckers and, to get it, they had to defeat the other applicant in a truck race. Their opponent invoked the trope, which allowed them to take the lead, then they invoked the trope, which allowed the opponent to regain the lead.
In the Looney Tunes cartoon "Tortoise Wins By A Hare," Bugs Bunny's attempt to win the race against Cecil Turtle by cheating backfires gruesomely: he has his underground buddies wait near the track to beat up the turtle when he comes along, not having told them he's also putting on a turtle suit that supposedly makes him more aerodynamic. Meanwhile Cecil is wearing a rabbit suit, so he isn't totally playing by the rules either, and he cheats more than Bugs in other cartoons where they race. Bugs' only case of the trope was stopping to put on the suit despite already being faster than Cecil. The ones beating him up only wanted to stop the turtle because they waged a lot of money. In no moment it was stated Bugs was even acquainted to any of them before the race.
Super Secret Secret Squirrel was involved in a road race against a conceited Southern rooster named Hot Rodney, who hedged his bet by kidnapping Morocco Mole. Secret Squirrel rescues him but not before holding Rodney up at a staged red light. As the race resumes, the heroes are in the lead but Rodney is catching up. Morocco jettisons everything from Secret's car—including the engine, which allowed Rodney to win. But the good guys get the last laugh as they give Rodney the booby-trapped belt Morocco was strapped to earlier.
Inspector Gadget has a Wacky Racing episode called "Race to the Finish." At the end, Dr. Claw tries to win by converting his car into the MAD Jet... and succeeds, only to be disqualified when the announcer pointed out that his car wasn't touching the ground.
Filmations Ghostbusters has a unique example in "The Beastly Buggy", another racing-themed episode. It's the end of the race, and the Ghostbuggy is neck-to-neck with Beastly Buggy. Mere yards before the finish, the ghostly Hot Rod decides to use the turbo boost... and runs out of gas right at the finish line, allowing the Ghostbusters to win the race. Unique in that Hot Rod wasn't technically cheating that time, even after he spent the whole episode using dirty tricks.
The Dexters Laboratory episode "Dexter's Wacky Races" has Mandark in the Dick Dastardly role with the show's other cast members (including Monkey, Agent Honeydew and the Justice Friends) as the other racers.
Borax Karoff does this in the 1936 Porky Pig cartoon Porky's Road Race. Zig-zagged as Karoff maintains a healthy lead throughout the race, stopping occasionally to pull dirty tricks.
Lampshaded/spoofed in a Tom Slick short: when asked by his flunkie what could be more important than winning, the Dick Dastardly Expy says "CHEATING!", even striking a lovelorn pose.