Jaron Namir delivers one to Adam Jensen at the beginning of Deus Ex: Human Revolution. The beat-down is so bad, it forces Adam to become augmented in order to survive.
Everyone in Dead Island has some form of this, but Sam B has the most literal one, where he cracks his knuckles and goes fists-a-blazing into the nearest undead horde.
The Walking Dead features Lee delivering one of these to Andrew St John. Considering his actions beforehand, it's an immensely satisfying moment for many. The player does have the option of stopping before his face is reduced to a bloody mess, but it's fair to say few people choose this.
Season two of The Walking Dead Sees a return of this trope with Kenny as beats Carvers face to a bloody pulp with a crowbar, in as revenge for the latter previously Beating Kenny into unconsciousness, and crushing his left eye-socket, destroying his eye.
Also in the cutscene just before the final boss fight, when Ocelot straddles Snake and starts pummeling him until he needs another stimulant injection.
Captain Price delivers one to Khaled Al-Asad in Modern Warfare 1. If you look around during the beating, the other hardened SAS officers — who've fought their way through hundreds of enemies to capture Al-Asad — keep having to look away.
And General Shepherd to Captain Price at the end of Modern Warfare 2. He'll actually kill him if you can't stop the fight in time.
At the end of Modern Warfare 3, Price delivers one to Makarov culminating in his death. It's immensely satisfying.
Jack to Andrew Ryan in BioShock. Andrew uses a posthypnotic command word to compel Jack to beat him to death with a golf club, to demonstrate that Jack has no free will. It might also be a form of Suicide by Cop, however.
In Bioshock Infinite, Booker delivers a particularly satisfying one to Comstock using the baptismal font.
Eternal Darkness has a villain-on-villain version in the battle between the rival Eldritch Abominations Ulyaoth and Chattur'gha. While each of the gods' battles have a pretty clear winner (due to the three gods having a Tactical Rock-Paper-Scissors relationship), there is at least a fight. Ulyaoth, on the other hand, tears its enemy to pieces through use of Portal Cuts, so Chattur'gha starts the fight by getting blasted with its own fireball, and ends by trying to crawl away on what remains of its limbs before being chopped in half by another portal.
Every battle in Dwarf Fortress ends in one of these if the loser doesn't get cut in half and sent flying across the screen or lose his internal organs to a crossbow bolt. The only other end is a creature getting knocked out and methodically dismantled by his opponent.
And then there's the undead. This being Dwarf Fortress, you could beat or wrestle with a bear or some other such worthy opponent until it capitulates, until the weather changes and suddenly your dwarves are being strangled by dessicated, individual bear limbs.
In early DF2010 releases, there were a few... bugs... with the new damage system not being able to effectively decide death conditions. Since combat will only end when one party is dead, the ensuing No-Holds-Barred Beatdown could easily continue for more than a season, resulting in every single bone and organ◊ in the victim's body being damaged until the combat system finally got around to calling them dead.
God of War III features this from a first person view. The first is from Poseidon's view as Kratos slams him around. The second is from Kratos' view as he beats Zeus to death with his own hands. And continues.
As you're doing this, blood splatters on the screen. You can continue indefinitely as the screen becomes covered in blood. The only way to continue with the game is to stop killing Zeus.
Y'know what? Pretty much all of the boss fights in God of War qualify.
In Gears of War 2, when an enemy soldier is in a downed state, you have the option to put your weapons away and punch the living snot out of them until they stop breathing in a satisfying scripted animation. Granted, they're already heavily wounded, and it only takes three punches to kill them.
In Gears 3, you're able to repeatedly tap Y to prolong the beatdown. For the COG, you repeatedly punch the enemy while they are down, like in Gears 2, but you can hold it for about 10 seconds, and it culminates with you punching their head into meat chunks. As a Locust, on the other hand, you rip off their arm and beat them to death with it for about 10 seconds.
Before his Face-Heel Turn into the series Big Bad, Sigma of Mega Man X was on the receiving end of one of these. A powerful Maverick was reported to be on the rampage and Sigma decided to deal with the threat by himself so that no one else would be endangered. Even though Sigma was easily the most powerful Reploid model at the time, the Maverick readily tore his sword-arm off and gouged one of his eyes out before beating him to a pulp. Sigma only won because of a "moment of weakness". Said event was actually what caused Sigma's Face-Heel Turn. And the Maverick? He became the hero known by the name Zero.
One of the Consume animations from Prototype is a very literal example of this trope. Mercer simply throws his luckless victim to the ground and beats the crap out of them until all that's left is a pile of easily consumed meat. Thankfully, all you see is the shower of bloodspray from the beating. The other Consumes aren't quite as literal, but are much worse since you actually get to see every gory detail. On a slightly less bloody note, it's possible to beat down a tank with the Hammerfist power. Mercer in general doesn't hold anything back when he fights.
In Half-Life 2: Episode 2, Dog does this to a Strider by jumping onto its head, punching it incessantly as it stumbles around, and finally tearing open its armored exoskeleton and pulling its brain out.
Dog also delivers another at the end, after Eli gets killed by an Advisor. Granted, the Advisors get away, but one of them's pretty badly wounded.
The backstory of Half-Life 2 had a huge example on a planetary scale: the Seven Hour War between the nations of Earth and the Combine. It lasted seven hours and...well, we lost.
Just about every sync kill in Dawn of War does this. Generally involves a unit pounding on its adversary several (dozen) times with a blade of some sort, then pulling out a ranged weapon and blowing it away. The Space Marines enjoy bringing an enemy to their knees and kicking them in the face with a giant armored boot, Commissars pull out a laspistol and do it execution-style, Dark Eldar Mandrakes just keep on stabbing. The variations are many.
This happens to Kreia in flashback in Knights of the Old Republic 2. Despite the violence in the rest of the game, this scene is the most visceral, consisting mainly of a large man beating the hell out of a defenseless old lady.
What makes it even more brutal is that she doesn't start a defenseless old woman. He literally beats the Force out of a Sith lord, until it is just a matter of beating the hell out of an old woman.
The Handmaiden also gets one at the hands of Atris near the end of the game in the form of lots of Force Lightning. Being a Jedi apprentice gave her what she needed to beat her sisters, but not a Master.
In The Godfather, this is generally what ensues when you render someone helpless by grabbing them. The sequel builds on this with Pummels and Executions.
In an example that makes up for its lack of gritty gore by sheer shock value, near the end of The Legend of Zelda: The Wind Waker, Ganondorf at one point just starts pummeling Link, showing every single reeling effect it has on the young child. Considering the light-hearted tone and graphical style of the game, it comes as a surprise.
The whole scene is pretty dark compared to the sunny, colorful artstyle of the game. It works incredibly well for it.
Although the flashiness masks the brutality somewhat, this is pretty much what happens in all combo videos.
The second game features a variation: instead of beating on Guybrush, LeChuck instead repeatedly stabs a voodoo doll of our hero.
The Curse of Monkey Island has another variation: instead of beating on Guybrush, every time they meet LeChuck hurls a fireball at him. Escape from Monkey Island is the only game in the series that doesn't end in a no-holds-barred beatdown, because it's instead a no-holds-barred stalemate, with the two sides able to slug it out forever without any result.
You can do this to enemies in Oblivion, since hand-to-hand attacks damage fatigue as well as health, and having zero fatigue causes enemies to fall over, after which you can gradually beat them to death while they're down. It takes a lot longer than just killing them normally, though. But since the game is full of monsters, killing them this way is very satisfying.
In Persona 3, there is a mechanic where enemies and allies may fall over after certain attacks. If every enemy is on the ground, the player is prompted to trigger an "All out attack," with the party members beating up on the damaged and off-guard enemies.
It returns in Persona 4, and in both versions it only works when both the Protagonist and at least one other party member are on the field and aren't incapacitated. If you finish off the enemy party with it, it ends in a giant skull-shaped mushroom cloud.
Johnny Gat of Saints Row delivers one in the game's sequel. After Shogo, the so-called leader of the Ronin, shows up at Aisha's funeral demanding a fight, the player character chases him down and drags him to a very pissed off Gat. Gat then delivers a smackdown on the punk, breaking his leg and punching his head through a tombstone. He then buries him alive. The lesson here? Do not fuck with Johnny Gat.
Virgo delivers this to the Phoenix in the middle of stage 7 in RefleX.
A direct allusion to this trope by Maya Schroedinger (Wild ARMs 3), who says this to Virginia after saving her and her party from Asgard (who did OHKO them): "I, Maya Schroedinger, will crush you to the ground, no holds barred. Just remember that."
In the prequel to Dissidia: Final Fantasy, Duodecim, this is pretty much Feral Chaos's EX Burst. Most everyone else gets a flashy standard attack for theirs... but Chaos is given twenty seconds to beat the crap out of the opponent before delivering the final blow.
Shao Kahn has one of these at the beginning of Mortal Kombat 9 against Raiden. The fight is mirrored at the end, before the final battle.
Ultimate Mortal Kombat 3's home editions introduced Brutalities, which were specific 11-hit sequences of punches and kicks.
In Metroid, Samus delivers one to Mother Brain during the mother of all Mama Bear moments at the end of Super Metroid. After what Mother Brain did, she completely deserved it.
In Shadow of the Colossus, the Colossi normally wait to attack if Wander has been knocked over and is lying on the ground. On Hard mode? No such luck. This can be particularly painful when fighting incredibly aggressive Colossi such as Celosia or Dirge, who also happen to have massively powerful charging attacks.
In Tales of Graces, the first time we are made aware of Lambda's presence is when Richard is attacked by a soldier, appearing to have been killed. However, Richard eerily rises up from the ground and proceeds to mercilessly cut the man down. The rest of the party can only look on in horror before Asbel eventually makes him stop.
In the "House of Horrors" quest in Skyrim, Molag Bal has you beat a helpless captive priest of his rival Boethiah to death with a rusty mace. Then Molag Bal resurrects him so you can beat him to death again to force the priest to renounce Boethiah and give his soul to Molag Bal. Then you beat him to death one last time. The beatdown empowers the rusty old weapon and it becomes the legendary Mace of Molag Bal.
After defeating Diablo for the final time, your objective changes to "Destroy Diablo". What that essentially means is that you get one minute of unloading whatever attacks you desire on his dying body.
In the Stage 2 boss battle of Time Crisis 4, Captain Rush receives this from Jack Mathers.
Happens right at the end of Fur Fighters. Just after the player has defeated Viggo, he comes back. Rather than using clever gadgets, schemes, or 100's of disposable mooks; he's decided to take matters into his own hands.
Probably the whole premise behind the single-player mode of Toribash, where a passive uke (no, not that kind) can be wailed upon by the player until they are reduced to flailing, blood-spewing bits with no resistance. A fair number of Toribash videos demonstrate new and creative ways to bash the uke into as many component pieces as physically possible, or simply find new ways to remove limbs.
Asura's Wrath has you doing this to pretty much every boss, including the creator of the universe who's been masquerading as a god.
Lara Croft is on the receiving end of an absolutely savage one midway through the 2013 reboot. After slipping into the Solarii stronghold where her friend Sam is due to be sacrificed to Himiko, Lara tries to break up the ritual by shooting the mook about to immolate her. Before she even has a chance to take another shot, she's grabbed by other cultists, thrown to the ground, and brutally beaten by half a dozen mooks while lying helpless on the ground. By the time Mathias stops the assault and Lara is dragged to her feet, she's nearly unconscious, unable to stand, and her face is a bloody mess.
Fate/stay night, "Heaven's Feel": The climactic battle between Shirou and Kirei is a brutal fistfight between the two, with the intent on both sides being to beat the other until they die. Ultimately Kirei dies due to injuries he sustained before the fight began.
From video game publisher Technos Japan (creators of Double Dragon) that helped define the Beat em' Up side scrolling genre comes the "Kunio-kun" series. The first title in the arcade line up? Nekketsu Kōha Kunio-kun (roughly translates to "Hot-Blooded Tough Guy Kunio") which only spans four levels, and for newbies, it can be this until you get the hang of the control schemes. Also worth mentioning is the infamous home consoled sequel Downtown Nekketsu Monogatari (Tale of Downtown Nekketsu). When it shipped overseas to Western release, it was released under the name "River City Ransom".
In Mass Effect 3, Kaidan or Ashley (which one is dependent on the events of the first game) receives an absolutely ruthless one from Eva Coré, the robotic infiltrator drone leading the Cerberus assault on the Prothean ruins on Mars. It nearly kills them, putting them out of commission for the first third or so of the game.
Kingdoms of Amalur: Reckoning has these in the form of fadeshift finishing moves; each finisher involves the Fateless One beating the ever-loving shit out of his/her opponent, then finishing them with various weapons crafted from the threads of Fate itself, including shooting them with a bow, impaling them on a massive sword, and even smacking them with a giant mace like an all-star baseball player.
Gunpoint lets you do this to guards you tackle to the ground. You even get an achievement for punching someone a hundred times!