A place in the story of a video game where it permanently becomes impossible to revisit earlier areas. Any optional sidequests or items (e.g. the Infinity+1 Sword) are effectively Lost Forever from here on out.
This often happens near the game's finale, such as before entering The Very Definitely Final Dungeon or just before challenging the Final Boss. You may even hear the narrator or another character warn you that "there is no going back" or "This Is the Final Battle".
There may or may not be Save Points, Trauma Inns, or item shops past the Point of No Return. If there aren't, crossing this point without sufficient resources (health, ammo, etc.) to survive the challenges ahead can result in the game becoming Unwinnable — especially if there's a Save Point beyond it, but no other means to heal or restock supplies.
The Point Of No Return comes in multiple flavours which basically correlate to points on the Unwinnable by Design scale:
Merciful: The game warns you that the point of no return is ahead. You are encouraged to save the game before heading out, and to keep that slot preserved in case you need to go back. (If you neglect this advice, you will put yourself in either a Tough or Nasty situation depending on the game).
Tough: You're playing through the game, and save your file as normal. Then you decide to go back to check something out. Hey, what the? There's no way back? But there's stuff back there you wanted to get... in fact, you left your good weapon back there and you don't have any ammo, and you already overwrote the file! Why didn't the game warn you?! However, there is a shop and the enemies here drop gold, so you can grind what you need to finish the game.
Nasty: Same as Tough, but there is no useful grinding opportunity and you have to win with whatever you brought with you. If you left your good stuff at home, then you'll either have to fight a much harder endgame than you should, or start all over again.
Cruel: Same as Nasty except there is no hint at all, even for Genre Savvy players (e.g. you don't appear to be heading toward the final battle at all), and/or the game only lets you save to one file, and encourages you to do so after you've passed the (hidden) point.
Another dimension to this trope is whether there is a Playable Epilogue or Endgame Plus that lets you go back to the rest of the world again after you finish the game. Even if you can, it's cold comfort if you're trapped in the Very Definitely Final Dungeon with no way to go back or finish it.
Games that regularly prevent you from returning to earlier completed areas are another trope entirely, although freeform or ability-based level exploration may blur the line. See also Plot Tunnel, which occurs mid-game and cuts off all the plot-irrelevant levels temporarily, until the current story arc is cleared.
This trope comes from the term used in air travel where after a certain point it becomes impossible to turn around and return to the point of origin (for example, not enough fuel); even if there is a sudden emergency, the plane must continue towards its destination.
Before going into the DXI ruins in The Nameless Mod your Mission Control will let you know that exploring the ruins will take some time, and that if you got something else to do before hand, now is the time to do it.
In Kings Quest V you must ride a sled over an ice chasm. The sled is very old, so it shatters on impact. You're stuck on the far ledge, so if you forgot something you're gonna have to revert to an older save file. That's hardly the only one, though. The desert cave is a point of no return too (you can only enter once), as is the Forest of Doom at the beginning, and the Ice Castle, and the beach after the giant bird, and the harpy island, and the final island, and the dungeon maze on the final island. Of course, most of these require you to have obscure items from earlier parts of the game.
Kings Quest VI has several of these. Once you enter the Labyrinth, the Land of the Dead, or the Castle of the Crown, you have to complete the respective sub-quest (or in the case of the Castle, the game). Worse, there are several points of no return within the Land of the Dead itself, so several things are easily Lost Forever if you don't get them before you move on.
In most installments, the point of no return is a Big Door that will warn you pretty clearly of that fact. The one in the first game is in a room called "Final Rest" (which comes after a room filled with several waves of enemies), just to make it absolutely clear.
Birth By Sleep notably doesn't do this, at least not overtly. It pretty well implies that the final boss is at Keyblade Graveyard but upon going there you can still run around and leave until you enter an otherwise unimportant looking area which will immediately thrust you into your respective character's Final Boss fight with no clear forewarning (unlike other games in the series which outright tell you "Entering here will start the final boss fight"). Though to get to the final boss, you have to walk through a long foreboding tunnel. Likewise once you start the final chapter of the game, you can't return to Radiant Garden without starting the True Final Boss battle upon entering so if you need synthesis items from that world you're out of luck.
358/2 Days subverts it twice. You're warned that "there may be no going back" right before Roxas leaves the Organization, but all it does is set you on your mission immediately after a cutscene. After that, Roxas starts off in Twilight Town instead of The World That Never Was, but you can still access the shop and all your previous missions before you face the Final Boss. The warning before that fight is subtler, but there's nothing stopping you from going back for 100% Completion after the credits roll.
Final Fantasy VI has a Point of No Return for the first part of the game; once you start the cutscenes involving the activation of the Statues/Warring Triad and the Emperor's death, you can't get back to the World of Balance because it's destroyed, meaning any enemies you didn't encounter yet or items exclusive to it (which admittedly isn't that many) are Lost Forever.
The Fort Condor battles each take place at certain points during the plot of the 1st and 2nd discs, often in very small timeframes. Advancing the plot before completing the battle will force the villagers to defend themselves, depleting their funds by 3,000 gil each time, and leaving the player missing out on any item or equipment reward they might have earned. Only the final battle is part of the main plot and once completed no more battles can be fought there.
Flying over Midgar at the end of disc 2 (to parachute into it) is another big one, for it marks the last time you can do the Wutai sidequest, as well as fight an optional battle with the Turks, and generally return to disc 2 (it ends in Midgar, and you can't leave until you finish it).
In Final Fantasy VIII, there are two major points of no return. The first one is the room past Mobile Type 8, where you fight Seifer for the fourth time. Once you fight Seifer, you cannot exit Lunatic Pandora until Time Compression occurs, by which point most major locations will be sealed off. The second one occurs just before Ultimecia's throne room; passing this point begins the very long Final Boss battle.
In Final Fantasy IX, you cannot return from Terra until you finish the plot arc there, and by the time you do, you're on disc 4 - some areas are locked off (as in the previous game). The game is merciful enough to warn you of this fact.
Earlier on, when you hit the final switch to exit Fossil Roo on the Outer Continent, the game warns you that you can't go back that way. You are stuck on the Outer Continent for the remainder of the disc.
On disc 3, you are tasked with finding the Desert Palace (arguably a Disc One Final Dungeon in its own right), and equipped with a ship to do so. Once entering, you are captured by Kuja and forced to take his airship (which you don't control) to the Forgotten Continent. And of course, you can't leave until you finish the somewhat difficult dungeon there.
You can go all the way to the end of Memoria and the showdown with the Big Bad (he is actually the penultimate boss), beat the snot out of the dragon-monster he throws at you, then just turn around and save or even teleport out entirely as long as you don't try to talk to him (which would trigger the final boss fights). He's a patient guy it seems and will just float around waiting for you to come back before trying to unmake all of creation.
Subverted in Final Fantasy X-2. Approaching the portal in the Farplane Abyss triggers a "Continue forward?" option, with the implication that this is the Point Of No Return. However, there is a save point further on where you can return to the airship, and you can in fact fight the first couple of stages of the Sequential Boss and still return.
In Crisis Core, the end of the eighth chapter is the PONR. Better unlock the missions that need to be found in Midgar first, for you're never coming back past this point.
Final Fantasy XII doesn't have any save points in the final area, although it makes sense since the final area only consists of at least 3 or 4 rooms. The game clearly warns you that once you go for the final area, you cannot go back, probably a first in the Final Fantasy series. Not only that, but saving at certain parts of the game will have the game advise you to save to another file if you are in a certain point in the plot where you can't go back for a while.
In Final Fantasy XIII, you generally can't go back to any previous location once you enter a new chapter (or sometimes, progressing far enough in a chapter). The only exceptions to this rule are Gran Pulse (Chapter 11), parts of Eden (Chapter 12), and the first area of the final dungeon (Chapter 13).
Final Fantasy Tactics has Nasty ones in multiple places—you can go back afterward, but it's possible to save the game and get yourself stuck between very difficult fights with no way to regroup, buy new equipment, or grind levels. The infamous Riovannes Castle portion, for example, puts you in three battles in a row, and lets you save between each of them. The first is standard fare, but the second is That One Boss at best, and flat out Unwinnable if you don't have the right equipment or skills. The third is a Luck BasedEscort Mission—if you don't have some speedy characters handy, it's not just possible, but very likely that you will lose before you ever get a chance to act. Even if you are prepared, it can be maddeningly difficult because of the suicidal AI of the person you're trying to protect..
The inside of Lavos in Chrono Trigger may or may not be one of these, depending on your method of ingress.
Baten Kaitos Origins has a Nasty one. Right as you're heading to a new continent (you've done this few already), the game prompts you to save, and suddenly the game prompts you to put in the second disc of the game. Other than the save prompt, this is completely unexpected, as there wasn't a Disc One Final Dungeon and your approaching the continent seemed normal. After a few cutscenes, you have to fight the Holoholobird, who also doubles as a Flunky Boss. You can't go back and grind or get new items, because the disc just changed. Many a player has been forced to restart their game to get around this.
Psychonauts has an Autosave of No Return (that's what an in-game prompt actually calls it) near the end of the game immediately after you free Lili. Luckily, it's saved as a separate file, just in case you weren't totally ready to sneeze your own brain out and enter a creepy mishmash of yours and the bad guy's childhood fears.
You can still revisit any of the previous levels to collect missed goodies for 100% Completion, though. Just be sure you cleaned out the hub level or you're boned.
Xenogears has a few of these. The first is Babel Tower, the PONR for getting a number of useful rare items from a certain shop (the only one that carries them, naturally). The second is before entering Solaris; continuing after that point denies you access to the world map until the very end of the game.
In Resident Evil Code Veronica, the point of no return is after leaving Rockfort Island. There's a metal detector deposit box on the island that isn't connected to the item boxes, so any items left here are Lost Forever once that part of the island is destroyed by the Self-Destruct Mechanism. Also, don't leave any important weapons in Claire's possession when you switch back to her for the last time.
Resident Evil 2 has its point of no return when you descend the turntable lift to the underground research facility, and again when you take the emergency elevator to the train platform in the B scenario.
Resident Evil 4 also has many of these, usually caused by broken bridges, such as after leaving the village, sealed doors, which may occur between chapters, or other one-way travel devices, such as the boat to the island.
Mario & Luigi: Partners in Time uses and subverts it. Right before the final bosses, your talking suitcase warns you that it's the point of no return, but at any save point thereafter, he gives you the option of going back in time to before you passed the point.
Metroid Prime 3: Corruption does this before The Very Definitely Final Dungeon. Its method of forcing this on you is rather unique though: ostensibly you could leave if you wanted, if not for the fact that mutagenic radiation on-site has corrupted your DNA so badly that your spaceship doesn't recognize you or even let you onboard anymore, so you're stuck until you take care of the problem.
AU 242: Take heed, Samus. Once you join the fleet and the wormhole to Phaaze is opened, there is no turning back. Please be sure to prepare yourself. We wish you the best of luck.
Super Metroid has a particularly nasty case: The Point of No Return is before the final save point in the game, so if you're aiming for 100% Completion, don't have that yet, and use that save point anyway...
Metroid Fusion also has a Point of No Return in that your ship's AI locks almost the entire space station down when it's time to fight the final boss. This is incredibly annoying for players trying to achieve 100% Completion, especially since you had little advance warning. Luckily, the game plays it fair by allowing you full access to the station again once you've defeated the boss.
Metroid: Zero Mission subverts this. At first it appears that Samus cannot get back to Brinstar and its surrounding areas after crash-landing in Chozodia. However, she can get back by using a Power Bomb on the glass tube connecting the Mother Ship with Chozo Ruins.
In Ōkami, before the boss gauntlet, Issun literally tells you you're about to step into "the point of no return", with that exact phrasing. The funny thing is that the game fakes you out with two of these before the two fake final dungeons before the real final dungeon.
There's a save point beyond the final and literal point of no return. If you save there and don't have a backup save that's outside of the area, you're trapped in the final dungeon until you begin a new game plus.
Issun is also your standard "boss battle ahead" indicator — stopping Amaterasu to ask if she's really ready just before you charge into danger.
In Okamiden, the Point of No Return is falling through the trap door in the Moon Cave 100 years in the past.
Neverwinter Nights has one of these, and frustratingly doesn't let you know until after you've entered the door.
Neverwinter Nights 2 seals some, but not all, areas during the transition from Act I to Act II, and likewise from Act II to Act III. In Act III, speaking to Nevalle to trigger the siege of Crossroad Keep propels the player into the endgame sequence.
Averted in Drakengard. Giant babies may be eating every person alive at the point you are in the plot, but you can go to any point in the story and play it again, no problem. In fact, this is necessary to get the other party members. You deliberately have to go back and replay certain scenes after a period of time to unlock a few of them.
Subverted in The Legend of Zelda: Phantom Hourglass. After completing the 13 (or so) level dungeon, you cross a bridge which crumbles behind you. Your fairy, Celia, says you can't go back now, and then a portal to the start of the dungeon opens up. In the sequel, if you save after the train segments in the Dark Realm, they are Lost Forever, including a very cool train Boss Battle.
The Ganondorf battle in Ocarina of Time. If you save here, there's no going back, as it immediately restarts at the cutscene when you reload. If you're low on life or magic potions or other items, God help you.
However, saving after the "gathering of the Triforce" cutscene results in the full version of said cutscene being Lost Forever, replaced with a shorter version*
(Ganondorf turns around, says two lines and the battle begins, without Boss Subtitles while he floats)
. While not as bad as other offenders, it's still a pity. On the other hand, people who have died and want to quickly go back to the battle get spared having to go through it again, saving some annoyance.
Played with in The Legend Of Zelda Twilight Princess when you enter the shadow-infused areas. Midna will tell you that you won't be able to return for a while. The way back to the world of light is closed to you once you enter the shadows, although you can teleport out using Midna's power, retaining your wolf form, and you can regain your human form by cleansing the shadows from the area.
The final level of Ratchet: Deadlocked involves a Point of No Return when you attempt to infiltrate the heart of Dread Zone Station to confront Gleeman Vox once and for all. Somewhat justified in that, well, once you leave you won't be able to use Dread Zone as your base of operations anymore, not to mention that pesky detail that the entire place explodes because Gleeman laced it with 'six gigatons of nitroglycerin'. This is the "No more save points" variety since you still get a weapons vendor right at the very start (and after you defeat Vox, you get to either start a New Game Plus or go right back to just before you left), but you can still get "stuck" here if you didn't grind enough earlier to max out your weapons / ammo / nano.
Though you can "cheat" by reseting your console. In that case, the game brings you back to the hub, and you can resume the final mission from right after the last mainframe destroyed.
Little Big Adventure 2: After landing on Zeelich for the second time, there's no way of going back to Twinsun.
In Mega Man X Command Mission, once you enter the final chapter of the story, you can't go back until you beat the final boss. On the plus side, beating the game DOES unlock extra armors for X and Zero in the end to retrieve.
In The Elder Scrolls IV Oblivion, returning to the Imperial City with Martin and entering the Elder Council chamber triggers the final fight sequence. From that point on, you either complete the main quest or you die. Completing the main quest immediately causes every other Oblivion gate to close, so you can never retrieve the powerful Sigil Stones or other treasure they contain.
The last dungeon in Daggerfall, the Mantellan Crux, would be considered a Point of No Return, if it weren't for teleport spells. There is no portal inside the dungeon and the only way out is to complete the main quest by collecting the Mantella. Morrowind seems to pay homage to the Mantellan Crux with the Chimer stronghold, Indoranyon.
It is a horrible idea to use a Teleport Spell to leave the Mantellan Crux since you won't ever able to go back in, therefore you can never finish the game without using cheats.
Skyrim has the Skuldafn temple as this. The only way to get there is by riding a dragon, and he tells you he can't stay there.
In Golden Sun you can save during the scene after you beat the final boss, which prevents you from doing anything else in the game. The second game does not allow you to save during that scene.
There's also a temporary version in the first game; it's impossible to go through Mogall Forest in reverse, so once you've left it the only way back to earlier areas is to pass through Lamakan Desert.
Golden Sun Dark Dawn drew much criticism for having no less than three of these, making just under one third of the Djinn and half the unlockable summons Lost Forever.
Four. The second one is often ignored because almost everything that gets locked out after you hit it becomes available again once you've passed the fourth one, and there are in fact some items that require you to return to those areas after the Grave Eclipse to obtain. Technically you could even call it five because the Cloud Passage (just past one of the points of no return) can't be returned to once you've left it, but the only treasures in that area are items that can be bought cheaply at any shop, so there's nothing really lost if you don't clean it out while you're there.
In Ys VI: The Ark of Napishtim, the point of no return occurs when you ride the Wyvern from Kishgal to the Ark(also The Very Definitely Final Dungeon). Any sword upgrades or items you missed will be Lost Forever, god help you if you don't have an extra saved game, as the boss fights may be rendered Unwinnable. Good thing Olha tells you beforehand.
These games also often prevent you from using Warp Wings or Warp Magic to make it a true point of no return. Averted in Ys IV: Mask Of The Sun, where you can still use the warp wing after jumping off the Iris Tower into the Golden Temple, which you can't otherwise return from. The raising of the ancient city does partially play this straight, as it destroys some previous locations such as Fire Mountain.
Darm Tower in Ys I & II. Averted in Book 2, where you can use the warp magic to return to previous areas even after entering the final dungeon.
In EarthBound, you cannot turn back after you enter the Phase Distorter II and attempt to teleport directly to the Cosmic Horror. Oddly enough, entering the Phase Distorter III (essentially a time machine) shortly thereafter is more hyped up as the Point of No Return, what with you being transformed into robots, the whole concept of Time Travel, and even the line "There is no turning back now," though that's probably because you run into a save point immediately afterwards. However, Dr. Andonuts does at least stress "You might not be able to return. So, make sure you are optimally outfitted" before you enter the Phase Distorter II.
In Earthbound's sequel, Mother 3, the game's final chapter is also a point of no return. The exact time it activates is when the vines guarding the sixth needle are removed, which can be done anytime after the preceding boss. After defeating said boss, anything that you want to do must be done before moving on with the plot.
That final chapter even has its own Point of No Return within it, which happens when Lucas and company fall down a ridiculously long elevator shaft in the Empire Porky Building after defeating the Porky-Bots.
In fact, every chapter in the game serves as a point of no return, due to the constant plot advancement where Nowhere Island is constantly changing, following the events caused by the Pigmask Army. This however, makes it harder to obtain certain items (like the Mystical Shoes or the Friend's Yo-Yo) and complete the Battle Memory, since some enemies are only available during certain chapters.
Even Earthbound Zero has a borderline point of no return. A word to the wise: do not talk to Queen Mary with all 8 melodies in tow unless you are sure you can defeat the final boss, as Magicant disappears once you talk to Queen Mary to teach her the song. If you lose to the final boss, certainly do not save or you will have to fight through the mountain full of Demonic Spiders to reach him again.
After a certain point in the Shibuya River in The World Ends With You, you cannot go back. In fact, you can't save after that point, either, because there are no enemies between you and the Final Boss, which means no Level Grinding if you can't beat him. Appropriately, the cutoff room is called "Rubicon."
In Shadow Of The Colossus, on the way to the last colossus, Wander's horse falls into a ravine, stranding you on one side of a gap.
In Sonic Unleashed, Chip warns you that once you go into Eggmanland, the only level of the game that doesn't have a hub your first time going there, you aren't coming out for a while.
Sonic Chronicles is worse. Enter Metropolis Zone and you're not coming back, allowing you to miss picking up Cream the Rabbit. Enter the Twilight Cage, and the same thing happens there, and you can miss Omega for it. Ditto for entering the Nocturnes lair, and a fifthPoint of No Return occurs when you go to fight the final boss. Thankfully items and rings (though not additional party members) carry over, into New Game Plus allowing you to get everything you missed, or miss it again.
In the earlier Sonic platforming games, getting close to the end of a level limits the camera scrolling to that area, making the player unable to backtrack. Sonic CD used a sign before the goal posts to mark the point in which this happens.
BioWare games often have a Point of No Return in the final act, where all incomplete sidequests and previously visited areas become unavailable:
In Baldur's Gate II, you could back out of the final locations right up until you engaged Irenicus in battle. After that, you were limited to defeating him, getting dragged to Hell together with him, completing several minor quests, fighting Irenicus and a few major demons again, and... watching the credits, in that order.
This carried through to the expansion, as you do return to the land of the living, but you can no longer access the areas from the main game. The only shared area is a Bonus Dungeon that is unrelated to the plot, but requires a fairly powerful party to complete..
On a side note, the first game allowed you to backtrack from every point of The Very Definitely Final Dungeon, up to and including the Final Battle, to visit the surface, heal, and buy more supplies, marking a complete aversion of this trope.
Knights of the Old Republic did this several times, with little to no warning before hand: accepting Canderous' offer to help you infiltrate Davik Kang's estate seals off the rest of Taris; finding the third Star Map seals off Dantooine; heading to the Star Forge seals off the rest of the galaxy.
In Knights of the Old Republic 2, going to the Jedi Council room on Dantooine after gathering together or killing the surviving Council members put you on a one-way track to the end of the game.
Mass Effect had a softer version. After discovering Saren's destination, visiting the Citadel temporarily sealed off the rest of the Galaxy, until you got the Normandy back under your command. The Citadel remained sealed off after that. Setting course for Ilos, however, put you on the one-way fast track to the endgame.
This, however, deserves to be explained in a touch more depth, as it really is a somewhat unique case. You're not told that getting the Reaper IFF will lock you in to the endgame, and unless you've consulted a guide beforehand, you might not know that you'll have just perhaps one mission of relative freedom left. Now, you obtain a new squadmate during the IFF mission, Legion. You'll want everyone to be Loyal to you during the endgame, so you'll spend your grace period doing Legion's loyalty mission. Once the Collectors invade the Normandy and kidnap the crew, you can either keep doing missions to get stuff you missed, or go straight through the Omega-4 relay, which as mentioned, is defined in no uncertain terms as the point of no return. So if you want your crew to survive, you'll do it right away. What isnt made clear (making this part potentially a little cruel) is that for every major ship upgrade you did not buy (exempting the facial reconstruction thing), one of your major squadmates will die on approach to the base. These are cutscene deaths; you can't do anything about it. Up to three, so if you neglected your upgrades, you may be putting yourself in a bad place from the jump. From there, you need to make a lot of hard choices about what squadmates to assign to what tasks in the base, and wrong choices will get your partners killed (in some cases, they could get killed anyway). And, of course, this is all the more stressful for any player who wants to import their Shepard character into Mass Effect 3, because every decision they make here has the potential to screw up their ME3 file (Your favorite character is Garrus? Too bad, you just got him killed and now he's not going to be in ME3!) unless they're willing to keep reloading the file before the game can autosave.
Mass Effect 3 has a two-stage "endgame", the first stage being the assault on Cerberus HQ. Admiral Hackett warns you that once you start, you're committed - there's no going back. After that mission, you go back to the Normandy, but you have only one place left to go from there: Earth.
Additionally, 3 had a minor (but fairly nasty) example; completing the Tuchanka arc causes Cerberus to attack the Citadel. After that, many available sidequests are permanently closed off.
From Ashes DLC: Finish Javik's recruitment mission without gathering all the Eden Prime intel? Better start a new game if you want that achievement.
Dragon Age: Origins also has a soft point of no return after starting the Landsmeet, upon which some quests and locations became unavailable. However, the real point of no return is travelling to Redcliffe after finishing the Landsmeet, which puts you, again, on a one-way fast track to the end.
Additionally, in Origins, securing the help of one of the factions for the coming fight seals off the town of Lothering, which, storywise, has been overrun by the Blight. Also, if you go to the Circle of Magi and agree to enter the tower, the doors shut behind you, forcing you to complete the quest line. You're warned about this, though.
Dragon Age II is merciful regarding the points of no return in the first two acts: Before starting the expedition at the end of Act I, you are told to resolve any outstanding business in the city. Before visiting the Arishok in Act II, Aveline tells you pretty much the same thing. Act III, however, ends without a warning: Accepting the letter which gives you the third main quest in this act, and then going to a certain part of the city triggers the endgame.
Fallout 3 contains a controversial point of no return in the final story mission Take it Back! Once the player enters the rotunda of the Jefferson Memorial, there is no way to exit. Activating Project Purity (or running out of time, causing it to explode) will result in the game ending, but because you cannot exit the rotunda, you have no choice but to activate it and receive an ending. In response to this jarring departure from the open-world nature of the game, modders took it upon themselves to design addons to allow PC players to continue their adventures in the Capital Wasteland after activating Project Purity. However, the Broken Steel DLC expands the main story, so regardless of your choice at the end, you can do sidequests after the main story's completion.
You can't play past the end of Fallout, although if you were fast enough, you could switch to turn-based combat and go into Vault 13.
Fallout New Vegas gives you a warning right before going into the final battle at Hoover Dam, asking you if you're committed to a specific ending. There is no option to play past the ending even with DLC, since the effort to implement the incredibly dramatic changes would be pretty astronomical for the developers.
Both Fallout 3 and Fallout New Vegas present Merciful points of no return early on. In these cases, after having played with your character for a bit, you're given a chance to reconsider your appearance, attributes, and skill loadout before they're committed permanently. You're allowed to back off and save at these points as an added precaution. Also in both games, when you're about to leave the main Wasteland and enter a DLC area, you're warned about the things you won't be able to do once your cross the threshold and given a chance to reconsider. The general warning given is, "Once you go, you can't return until you finish." However, in Lonesome Road you are able to leave The Divide even before you complete the storyline, although there is a point of no return when you enter Ulysses' Temple. Point Lookout also allows you to go back to the Wasteland if you can pay the ferry toll, and you have to return to the Dunwich Building for one of the sidequest objectives.
There's two tough Points of No Return in the Fallout 3 DLC Mothership Zeta. Once you go up to the upper level of the mothership, you can't go back to the lower level, and once you reach the Death Ray Hub, you can't go back to the preceding areas. Some areas can be revisited after completing all of the quests, but others, such as the Cryo Lab, Waste Disposal, Research Lab, Weapons Lab, and Biological Research areas, which contain many of the Captive Logs and a number of unique weapons, are Lost Forever.
As with Vault 101, once you leave Raven Rock, you're permanently locked out, and thus if you missed the Energy Weapons Bobblehead or other items, they're gone forever. Raven Rock itself has a point of no return when you enter the Control Room, immediately after you pass the room with the bobblehead.
During the Reilly's Rangers sidequest, there's a nasty one when you enter the Statesman Hotel through a one-way drop; you can't leave until you reach the rooftop and fix the express elevator, fighting through hordes of Super Mutants along the way. If you run out of ammo, you're up the Unwinnable creek.
Operation: Anchorage has several of the Nasty type, as the result of locking doors or invisible walls, preventing you from retrieving any Intel cases or weapon pickups you missed, or using previous ammo or health stations.
In Honest Hearts, once you start the final quest, you are warned that you won't be able to do any previous uncompleted sidequests.
Dead Money has one when you enter the Casino, and another after using the basement security terminal, which locks the elevator until Elijah comes down. After completing the story, you have one last chance to explore the Villa before returning to the Mojave.
After assembling the Golden Warpship in Solar Jetman, you can't go back and pick up any treasures that you missed on the last planet. You now have to fly the super-cruiser off the planet in one shot, and colliding with the planet's surface will kill you and end your game, since that warpship is the only one of its kind.
There are three points of no return in Illusion of Gaia: Getting on the Incan ship, going to the Sky Garden, and the cutscene immediately before Dark Gaia. You also cannot go back into Edward Castle after escaping its dungeon.
In Jade Cocoon, there is no warning that after completing the Moth Forrest you're cut off from any previous areas in the game.
Far Cry 2 has a particularly evil point of no return. The final mission briefing requires you to enter a prison to get your objectives. After you accept the final mission and carry on with the game, it warns you that you can't turn back if you go any further and to make sure you have everything you need, however if you try to go back, you'll find you can't leave the prison.
Grandia has a doozy at the end, where one scene starts a chain that prevents you from going to any previous area, and leaves you stuck with access to the final dungeon only if you save.
Quest 64 has one, sort of: at the end of a hallway in Brannoch Castle, there's a door to a room with Brian's father, battered from combat thanks to Shannon. You'll know you're in this hallway because halfway through there's a door leading to a room with Leonardo who provides an opportunity to rest. The only way to visit any previous areas if you go past this point is to die before saving again, so that you get sent back to whichever rest person you rested with last. Of course, Epona provides an opportunity to rest near the end.
The General Ross boss battle in The Incredible Hulk: Ultimate Destruction is one, for you will be thrown immediately into the next two story missions with no chance to freeroam in-between until you complete them since they involve the Hulk breaking out of the Vault and escaping his captors.
Quest for Glory II operates on a 30-day cycle. The caravan to Raseir leaves at dawn on day 17, and you are locked into the endgame for the rest of the adventure.
In the third game, it's after the Tarna peace conference with the Simbani and Leopardmen. After the Leopardman leader (possessed by a demon) and the Laibon kill each other at the conference, the gates to Tarna close, barring you from ever entering the city again. You also can't enter the Simbani Village anymore, thus railroading you to the jungle and to the Lost City.
In the fourth, it's the Dark One Cave once you finally enter it again.
And in the fifth, it's the mansion of the Big Bad.
In Avencast: Rise of the Mage, don't go through the shimmery interdimensional portal if you ever want to go back... despite the fact that the other end stays open, and every other such portal you encounter later can be used repeatedly.
Prince Of Persia games are built around this design in order to be linear. Doors will close behind you and lock, walls will crumble and block a pathway behind you, or you descend slopes or walls that are too sleep to climb back up again. Make sure you don't miss anything!
Wild Arms 5 has a Point of No Return that the game is kind enough to warn you about at the top of Volsung's TF System Tower, right before fighting Volsung the first time. Once you pass that point, you actually have several bosses and a whole Very Definitely Final Dungeon to run through, so chances are you'll want to save at some point...but if you do, you can't return to Filgaia until the New Game Plus.
Vampire The Masquerade Bloodlines lets you wander freely through unlocked areas right up until Griffith Park. Once you head off for that quest, you're locked into a sequence of three to four endgame missions. The game does allow you to buy blood, weapons and so on in between stops.
Pokemon does this with the Elite 4. You can save halfway through or whatever if you like, but you might find yourself in a losing battle where you won't be able to win. But once you go through the first door, you can't go back.
But if you lose, it just sends you back to the Pokemon center outside, and you can still go anywhere in the game after you win.
The first gen games also have a temporary example. After you leave Mt. Moon, there's a ledge with no ladders or stairs going back up. Once you jump down, you're effectively locked out of that area until later in the game.
In Endless Frontier, you can neither save nor leave after entering the Einst world. This means that you must win three boss battles in a row to complete the game, with no chance to save. Fortunately, Koma comes with you, giving you access to both a shop and a means of free healing.
Impossamole (the TurboGrafx-16 version) is particularly egregious; in addition to physical barriers preventing you from backtracking to get a Scroll that you missed, there are also Checkpoints of No Return, so the level becomes Unwinnable until you lose all your lives and restart.
In Persona 4, on the very last day, you can choose to chase the True Ending by entering The Very Definitely Final Dungeon instead of going home. If you do so, once you enter the TV world, you won't be able to explore Inaba anymore; if you try to leave, you'll only have the choice to go to Daidara or Shiroku (and even then you get a fade transition when you go to either, rather than walking there manually).
Averted in the Normal Ending. From the time that Adachi's dungeon opens, you can choose when to finish the dungeon and can return as many times as you want, regardless of your progress. Even if you put it off to the final playable day and then return home, you will get a Non Standard Game Over and go back in time instead of being forced to move forward.
Then again, one may argue that this ending's Point of No Return is chronological instead of physical: namely, 7 days before the final day to beat that dungeon is the point Igor can return you to if you get the Non Standard Game Over. If you haven't saved before that point, then, it becomes a Point of No Return.
By contrast, in Persona 3, entering the final dungeon on the final day is compulsory, and once you enter Tartarus, you cannot leave even to shop. During the final week, your characters continually remind you in bright red letters to stock up before that day arives.
The Fable games have several of these, and the player is usually explicitly warned about them, such as the final (or first, if you're playing The Lost Chapters) battle against Jack of Blades, as well as the lead up to the true final battle against him in TLC in the first Fable, and going to the Tattered Spire and then again later when meeting with Reaver in Fable 2. But then there is the infamous Day 121 in Fable 3, after which the game progresses immediately to the endgame with hardly any warning, and if you haven't put enough money into your treasury by that point, you're doomed to the bad ending.
Actually, in Fable 3, you can return very easily by turning around and walking into the fog, which sends you back to Day 121. Honestly, it's revealed just by panning the camera around.
In Assassins Creed II, at the start of the final Sequence you are given the option to go to Rome to hunt down Rodrigo Borgia aka Pope Alexander VI. Once you accept, you cannot return to the rest of Italy until you complete it.
Assassins Creed Brotherhood is more insidious; after a certain point in the first Memory of Sequence Eight, the game puts you on a roller-coaster ride straight to the end of Sequence Nine with no option of declining missions and resuming free-roam. Then comes finding the Apple under the Colosseum and the... nasty fracas that ensues. When you finally get back to free-roaming, while other sidequests are still open, you cannot exit the Animus to Monteriggioni any more.
Subverted in Assassins Creed Revelations though; while the Animus Island dismantles near the end, watching the credits will allow the Animus Island to rebuild itself, so you could play as Desmond in those platforming puzzles for as long as you like after you beat the game.
Finding the key in Assassins Creed III kicks you back to the real world, where you are forced to activate the planet shield in return for Desmond's death and releasing Juno into the world. However, after credits and Connor's epilogue, you can continue to roam the Frontier and the cities again, but you can't exit the Animus. In fact, at this point, you can play mini-games that require finding certain "pivot points" in the game world that are, essentially, cheats. Finding those is not easy and requires a lot of ground-pounding, especially since pivot points are placed by other players doing the same thing as you.
Tales Of Symphonia: Upon reaching the deepest level of Derris-Kharlan and witnessing the second-to-last scene of the game before the Final Boss, you can still return to the overworld—either the way your came or by solving a puzzle that opens a warp which teleports you back to the entrance.
Tales Of The Abyss: After you reach Eldrant and defeat Asch in a duel, and witnessing his You Shall Not Pass scene against the oncoming Replica soldiers in order to allow Luke to proceed and confront the Big Bad, it's still entirely possible to return to the world map.
In fact, in both games you NEED to view these scenes in order to unlock some sidequests in the games.
When you go to Tomorrow City for the second time in Epic Mickey, you can't go back to Mean Street. Also, you only get to climb Mickeyjunk Mountain once, the next time you go there, it'll be a different part of it.
Every time you leave a location in China in Shadow Hearts (with the exception of Shanghai), you leave for good. After Dehuai's tower, you leave China for good.
Left 4 Dead had very few of these, which weren't really anything major unless you missed a health kit or the like. If someone got incapacitated and everyone else had moved on beyond the point of no return, the helpless player can do nothing but bleed to death. The sequel adds many more points of no return, making these a strategy for infected players to use in VS mode.
Play Station Home has a hub in the list called "Xi Museum", which is essentially the ending point of the "Xi Virtual Reality game" run back in 2009. Players were allowed to wander around, play games, talk with people, visits random areas, and try and solve the games puzzles. When the player reached the monolith, however, they were given the choice to choose to break it or activate it, or not do anything. Choosing to break or activate it meant that you would never be allowed to do any of the listed actions ever again, forfeiting your world of Xi for awards and a cinematic involving Jesse. Not breaking it however led to the player never getting any awards, and when the virtual reality game was removed, the player was forced to leave anyways.
In Sailor Moon: Another Story, each part of the game is divided into arcs, and there are several areas you can never visit again if you don't get everything from them when you can visit them. This can be extremely annoying when trying to gather the sailors' character-specific equipment. If you missed Mars' Ruby Tiara, for example, you can't go back for it past a certain point in the game and you've therefore lost the large stat increase it gives.
In Shin Megami Tensei: Nocturne, there are two places where this happens. The first comes from entering the Tower of Kagutsuchi; if you're doing a Neutral, Demon or Reason ending then this is where your ending is confirmed. However, there is a second one which comes from clearing the Amala Labyrinth and being imbued with Lucifer's powers. If you trigger this one, then it overrides any other ending you would have normally gotten.
In Shin Megami Tensei Strange Journey, once you approach the Final Boss's room for the first time and speak to resurrected Gore, answer his questions (if you qualify for them by not being too extremely Law or Chaos), and kill him (if you qualify as a result of not aligning as Neutral), your Character Alignment is locked for the rest of the game.
In Bastion, you get a warning before you prepare to enter the Tazal Terminals. You're given plenty of time to complete any Proving Grounds weapon challenges you missed, but once you visit the Terminals, you can't go back, and you have to wait for a New Game Plus to attempt them again.
Deus Ex Human Revolution is Merciful. It tells you whenever you are about to leave an area for good and informs you that any side quests will be cancelled.
Not only that, but it also stores your last two auto-saves in the load menu.
And save slots which the game orders from most recent to oldest. Amount of said slots varies on your system.
The DLC, The Missing Link borders on cruel, however. There are about three spots that, when you pass, you can't return. It makes sense from a mechanical perspective, but there is very little to indicate that these areas are checkpoints. So, woe upon you if you wait to get some more augmentations before you try one of the achievements.
The first God Of War has a point near the end where the voice of Athena tells you that once you will not be able to return until you have gotten what you came for. This is a Merciful rather than a Polite example though, as even once you come back to where you started, you cannot go back to get stuff you missed.
Minecraft falls under the Nasty bit when it comes to visiting The End. Once you go in, there's no way to leave other than to jump off the world and into the void, killing yourself and losing all items on your person. OR, you can hope that what you have with you is sufficient to defeat the Enderdragon so you can find the exit portal.
Similarly, if a Ghast's explosive fireball hits your portal in The Nether, it shuts it off, trapping you in the hell world unless you were smart enough to bring Flint and Steel with you so you can relight the portal. If you don't have it, you can hope the Ghast will shoot the portal again to turn it on or you have to kill yourself to leave.
It's no longer possible to be trapped in the Nether thanks to the Fire Charge, an item that works exactly like the Flint and Steel and is crafted by gunpowder (gotten from Ghasts), coal (gotten from Wither Skeletons), and Blaze Powder (gotten from Blazes). However, if you are playing with generated structures turned off, it also prevents Blazes and Wither Skeletons from spawning since the Nether Fortresses are their homes, effectively locking you in the Nether should your portal be shut off.
In Metal Gear Solid 2, entering the holds in the Tanker chapter, and rescuing Emma in the Plant chapter.
In Metal Gear Solid 3: Snake Eater, after you defeat The End and climb that huge ladder to the mountains, Snake slides down a slope that is just too steep to climb back up. Later, the two trips to Groznyj Grad are both Points of No Return, as is retrieving Sokolov and confronting Volgin at the Shagohod maintenance room.
Completetly Averted with Radiant Historia since you can go back in time anytime you want to earlier in the narrative, so you can't miss anything. In fact, some sidequests you receive are so time-sensitive you've already failed when you get them, you must go back in time to meet the requirements.
This is also inverted. The two timelines have certain fixed Points You Can Return To. Some of these are a couple hours' play apart the first time you go through them, and going to Historia in the meantime will set you back to your starting point and reset your fast-travel options, forcing you to get back to where you were the hard way.
Quake II allowed you to move freely between levels in one of the several "units" (hubs) making up the bulk of the game, but once you passed through the exit of a unit you could not return (and the first time the game would warn you about this). Also, the teleporter in the Upper Palace was a more definitive Point of No Return—once you passed through it you went to the final boss arena on Stroggos' moon and could never come back. Unlike in earlier id Software shooters, this can be a problem because you could stockpile items for use later instead of using them the moment you picked them up. Left a Quad Damage behind? You're SOL.
In tomba 2, once you enter the door with the final pig gate, time will freeze and you can only do the main story. Thankfully, kainen warns you of this before you enter the door.
NetHack has one right before the elemental planes, but it warns you beforehand and there are opportunities (albeit limited) for items to drop.
In the XCOM: Enemy Unknown remake, entering the Gollop Chamber with your top psychic soldier will start the final sequence. However, the game is pretty merciful and warns you several times that you won't be able to do anything but attack the Temple Ship from that point on. Any ongoing R&D will stop, and no more UFOs will show up. In fact, the first time you try to do this, one of the characters will outright tell you that she feels that activating the Chamber will mark the beginning of the end.
A mild example of a "tough" Point of No Return in Evil Genius. One of the secondary objectives involves gathering four pieces of a totem, each of which has a a negative effect on nearby minions. However, if you get them all and put them near each other, they will combine into one totem with a strong positive effect. The problem (or a bug) is that the pieces will combine only on your first island. While the game doesn't force you to move to the second island until you're ready (although you still have to do it to continue the main storyline), it doesn't warn you about the totem thing either, which means you get stuck with four negative loots that can only be negated by putting them into a freezer (or if you get them stolen by burglars).
Wolfenstein places an arms dealer almost within sight of the point where you infiltrate the zeppelin, and helpfully informs you that this will be the last time you'll be able to buy upgrades or ammo.
Cave Story has a temporary one and a permanent one, both qualifying as Nasty and borderline Cruel:
The temporary one comes after being forced to kill Toroko, at which point you are trapped in the Labyrinth. You cannot return to previous areas until you beat Ironhead, who comes after four other boss battles, two of which are considered the hardest bosses of the game, Labyrinth M, the first area that is a consistent fighting area with no save points, as well as the start of the two sidequests that determine if you can get the true ending.
The permanent one is saving at the last save point in the game. After destroying the zombified Core, which takes the Doctor with it, the island will start to plummet. If you complete the two aforementioned sidequests, however, you can enter the house that acted as a rest stop between the Last Cave and the Boss Bonanza you just beat. However, once you enter, the door is locked, you cannot use the bed to heal, you have to go through the absolutely brutal final level and its two bosses without dying, and, perhaps worst of all, the bookshelf, which looks like it can bring you back to before the Boss Bonanza, only brings you back to after it. If you save here, you are completely stuck.