Specific example: Shortly after "Stone Cold" Steve Austin's infamous 'accident', The Rock was in a match with the Big Bossman. Bossman pulled his usual Heel tactics, which resulted in the Rock snapping and beating him, the ref, several MORE refs, and the paramedics into states that greatly resembled comas with anything and everything he had on hand. Leaving him standing in the center of the ring, staring about wildly with a pile of destroyed humanity all around him. The point was to cast suspicion on The Rock for Austin's accident, you see.
Another inverted example had a cage match between Vince McMahon and "Stone Cold" Steve Austin. Austin beat Vince so badly and so bloody the match had to be stopped and McMahon had to be wheeled out on a stretcher, but then Austin jumped on the stretcher to continue punishing his boss.
The Two Man Power Trip (Triple H and Stone Cold) delivered an absolutely hellacious beating to the Hardy Boys and Lita. It's pretty uncomfortable to watch, especially as they humiliate and destroy Lita with a chair... not that they needed the chair. 
After Kane unmasked, he turned on his former tag team partner Rob Van Dam. Inevitably when this thing happens between wrestlers, they get put in matches, in this case several, and Rob did nothing but get thrown, slammed, punched, choked, and stepped on. The only match in their series Rob actually won was a steel cage match, where you need to escape to win. When Kane tossed the helpless Rob through the cage, the referee counted it as Rob escaping. Upon his return in 2011, Kane has been dishing these out to John Cena, as well as his pal Zack Ryder.
General example: Any match involving one of the members of DX eventually devolved into this.
During the kayfabe (pre-mid 1990s) era, when most wrestling TV programs pitted top and mid-level talent against jobbers, a promoter would sometimes push a villain as an unstoppable Monster Heel by having him continue beating jobber wrestlers (and sometimes anyone else) well after they could have scored a victory. The idea was always to demonstrate the heel's power — and often, devastating impact of his offensive arsenal — and (the main goal) rally the fans to call upon the promotion's top babyface to demand a match with the heel and give him his comeuppance.
Back when they were getting their start in WWE, Jamal (Eddie Fatu, who would later become Umaga) and Rosey (Matt Anoa'i, Roman Reigns' older brother) formed a tag team called "Three Minute Warning". Eric Bischoff would warn people who were getting on his nerves that they would have three minutes to entertain him/make their case or he'd send these two out and they'd beat the crap out of his target.
In 2004, Antonio Inoki ordered Kazuyuki Fujita to deliver shoot kicks to Shinsuke Nakamura's face during a wrestling match and apparently unsatisfied with the results, came to the ring himself after the match was over to deliver more blows to Nakamura's face with his fist.
Though the referees stopped her before it went too far, at Survivor Series 2004, Lita was well on her way to unleashing one of these on Trish Stratus, having already smashed her face into a chair, the ring steps, beaten her with the chair, pummeled her in the face, and was choking her by the time several refs were finally able to pull her off. Even at that, she still managed to get away from them and go back for more.
Randy Orton was on the receiving end of these during a few of his battles with The Undertaker in 2005, most notably in a Hell in a Cell match. He also had his house broken into by Triple H (in Kayfabe, naturally), who proceeded to smash Orton against his own furniture, culminating with HHH throwing Orton through a window.
Samoa Joe delivered a brutal one to Christopher Daniels at the TNA Genesis 2005 show, the two were in a team elimination Match and they wound up winning but Daniels scored the pin which Joe had wanted. After a bit of arguing the two seem to coincide only for Joe to turn and knock Daniel's head out with a kick. He then busted him open with a chair shot with Daniels bleeding and semi conscious unable to do anything helpless before Joe's onslaught as he wound up delivering several Muscle Busters to him, one onto a Chair.
As if the Briscoes beating The Kings Of Wrestling 2 falls to 0 wasn't enough reason for a Title Drop at the 2006 ROH Domination, the main event saw World Champion Takeshi Morishima beat Roderick Strong's ass for over thirteen minutes straight.
The Nexus are infamous for giving these. Notable, as it's an entire group of seven people delivering these to an unfortunate victim. To say it's like watching a pack of wolves devouring their prey is, quite frankly, an understatement.
A non malicious example was the fourteen minute beat down "gravure idol" Yuzuki Aikawa got in her pro wrestling debut at Wonder Ring STARDOM from Nanae Takahashi, a veteran known for using other wrestlers as billy clubs. Since fans and fellow joshi alike were skeptical when STARDOM agreed to let a swimsuit model into the ring, Takahashi's thrashing was her way of having Aikawa "pay her dues" upfront, so that everyone else would leave Aikawa alone.
Jessicka Havok has twice had the loved one of her opponent throw in the towel, rather than watch how the match would play out. In WSU it was Alicia's mother. In SHINE it was Reby Sky's boyfriend.
The Shield (Dean Ambrose, Roman Reigns, and Seth Rollins) have been doing this to pretty much everyone they come into contact with since they debuted in late 2012. They claim it's in the name of "stopping injustice" but the end product has been little more than senseless violence (as they also claim to work for no one so it must be implied they choose their own targets).
Brock Lesnar, especially his match with Cena at Extreme Rules 2012, where Lesnar laid into Cena with numerous brutal looking knees and tossed him around like a chew toy. Cena somehow won this match simply by punching Lesnar in the face with a chain then throwing him on the steel steps. Brock Lesnar vs. John Cena for the WWE World Heavyweight title at SummerSlam 2014 made up for this above folly, seeing Cena get suplexed 16 times over the course of the match and mounting no real offense at all. In fact, Lesnar landed his finisher less than a minute in and could easily have pinned Cena at any point but wanted to continue until Cena threw in the towel himself before he got bored and pinned him after another F-5.
Triple H delivered a particularly vicious one to Daniel Bryan during the 3/17/14 broadcast of RAW. At first he called Bryan to the ring alone to talk regarding their upcoming match at Wrestlemania 30 and even admitted that he respects him to a degree. Cue Stephanie McMahon coming out and having the cops arrest Bryan for having occupied the ring with his fans the week prior. Hunter calls the cops off after they've put Bryan in handcuffs in a supposed gesture of sympathy...and then proceeds to absolutely beat the shit out of a handcuffed Daniel Bryan for about fifteen minutes.
Triple H also delivered a beatdown to Sheamus weeks before Wrestlemania 27 to get revenge on Sheamus doing the same to him the previous spring, and to send a message to his opponent for Wrestlemania, The Undertaker
Bryan would also attack Triple H from behind two weeks after the beatdown mentioned above while Triple H was on commentary during a match, complete with a kendo stick. Trips could barely get in a hit before running like a scalded dog a few minutes later, and even assistance from Randy Orton and Batista couldn't stop Bryan.
At NOAH Great Voyage 2015 Shelton Benjamin delivered a message on the behalf of Suzuki gun at Katsuhiko Nakajima's expense but immediately afterward Naomichi Marufuji did him one better by beating on Atsushi Kotoge for fourteen minutes.
Kevin Owens delivers a a vicious beat down on to his "Best Friend" Chris Jericho on their Festival of Friendship. Going as far as giving Jericho the Pop up power bomb on the apron and smashing his face against a TV.
On Jan.27, 2003's edition of WWE Monday Night Raw, Trish Stratus, having already lost a brutal Chicago Street Fight WWE Women's Championship match against Victoria, barely had time to recover in the ring when she was confronted by an angry and returning Jazz, who blamed Trish for putting her out of action for 7 months with an ACL injury and taking her women's title in the same night months prior. What resulted next was arguably the most brutal beatdown in the history of the women's division: Jazz proceeded to kick a still-down Trish in the face, laid out Trish with several of Jazz's signature moves, including a Fisherman Buster Suplex and 2 DD Ts that repeatedly knocked Trish unconscious, and locked Trish into her submission hold the STF for several minutes before referees finally pulled Jazz off the injured and defenseless Trish. As a result of the beatdown, Trish missed almost a month of action before she returned for her revenge against both Jazz and Victoria and won back the women's championship at Wrestlemania XIX two months later.
A heel Braun Strowman rose to stardom—and arguably became a babyface—thanks to his multiple beatdowns of Roman Reigns in 2017. Perhaps the most prolific example was during the April 10, 2017 edition of WWE RAW. Roman, already unpopular with many fans and getting booed even more after beating—and at the time, thought to have permanently retired—beloved wrestling icon The Undertaker at Wrestlemania 33, was in the middle of an interview discussing his win against The Undertaker when the bigger and stronger Braun came out of nowhere and threw Roman around like a chewtoy. It was thought to have ended when Braun smashed a crate into Roman's skull, causing Roman to require medical assistance. But Braun wasn't done. As the EMT's were getting ready to take Roman to a nearby ambulance, Braun commandeered the stretcher with an unconscious Roman strapped into it and threw both off a landing ramp several feet into a nearby garage. In some unintentional comedy, many fans in the arena showed no sympathy for Roman, chanting "You Deserve It!" at him, a chant normally used to shower heroes with adulation for winning their first world championships, but this time used to mock the unpopular wrestler's plight. After several minutes, the EM Ts had finally managed to load Roman into an ambulance to seek medical help for the injured Roman. But was Braun finished with him? No. Braun even shouted so as he returned, punched a still-stretchered Roman a few more times and then proceeded to tip over the ambulance with Roman inside. Roman was not seen for several weeks until Backlash, when he was still visibly bandaged as a result of Braun's attack weeks earlier.