Although not universal, it is a general convention of roleplaying games that the player is given access to a 'party' of characters. Alongside their protagonist, they have a group of other heroes who fulfil different roles within the party, often with their own interactions, dynamics, and storylines.
In games that do give the player access to a party, a clear way to make a level memorable is to take that party away. Injuring, imprisoning, or simply separating the protagonist's allies and forcing the main character to go it alone changes up the gameplay dramatically. It can create tension, difficulty, or poignancy.
10 Shepard Makes The Final Push Alone (Mass Effect 3)
The climax of Mass Effect 3 sees a massive ground force assault on a Reaper position protecting access to the Citadel. Things seem to be going Shepard's way until the Reaper Harbinger joins the battle personally, decimating the attacking force - including critically injuring Shepard's companions.
After spending the majority of Mass Effect fighting with two allies beside him at all times, Shepard has to board the Citadel alone and injured. This leads to a fight regarded as one of the most difficult in the series, against a mere three Husks and a Marauder. Shepard's injuries and isolation make him very easy to kill in this engagement.
9 The Exile Has Little Help On Malachor V (Star Wars: Knights Of The Old Republic II: The Sith Lords)
The story of Knights Of The Old Republic II's party ends where it began for each of them - on the ruined planet of Malachor V, site of the final battle of the Mandalorian Wars. Despite the entire party uniting to battle Kreia there, the Ebon Hawk crashes shortly upon arrival, with only the Exile getting clear in time.
The Exile has to fight their way to Trayus Academy and meet their fate there alone. In a variation, however, Knights Of The Old Republic also cuts away to sections playing as other members of the party. This includes Mira's duel with Hanharr, Atton fending off Darth Sion, and Bao-Dur's remote destroying the planet. In each instance, however, the player only ever controls one character at a time.
8 The Forgotten Cellar Is The Game's Only One-Person Dungeon (For The King)
For The King is a unique roguelike RPG where each party member is controlled separately, both in combat and on the overworld map. For The King's gameplay allows for one person to control all three, or for three players to each take control of separate characters. As such, any character can be isolated at any point, or even made to do dungeons by themselves.
There is only one dungeon in For The King, however, that makes it mandatory for one character to fight it, regardless of the party's actions. The Forgotten Cellar, necessary for the main quest in the game's first campaign, is a single-room dungeon with one fight. That fight is against a brutal enemy that can permanently destroy equipment. As such, it is one of the game's more notorious moments.
7 Chapter 13 Sees Noctis Isolated (Final Fantasy XV)
The party is a major factor in both the gameplay and the story of Final Fantasy XV. Much of the game's plot is four friends taking a roadtrip together. As such, one of the game's darkest hours comes when the protagonist, Noctis, must fight alone. After being tricked into throwing Prompto from a train, and being separated in a demon attack, Noctis must battle through Zegnatus Keep by himself.
In addition, Noctis loses his regular powers, and acquires new attacks from the Ring of Lucii. When Final Fantasy XV was first released, the combination of the loss of the party and the new combat mechanics proved controversial. So, this section was made far easier. Nonetheless, the loss of the game's typical camaraderie is sobering.
6 Llednar Attacks A Lone Marche (Final Fantasy Tactics Advance)
As a hybrid of a turn-based tactics game and an RPG, Final Fantasy Tactics Advance typically has larger parties than the average RPG engaging in battle. With a combat system based around positioning and synergy, it is not well-suited to duels or lone combats.
When protagonist Marche attempts to confront his friend Mewt at Bervenia Palance, he is left alone with the powerful enemy Llednar Twem. With no party to support him, Marche is already on the back foot. Things are made worse by Twem's total invulnerability. The result is less of a combat, and more Marche running for dear life until he receives help.
5 Almost An Entire Playthrough Is Spent Solo (NieR: Automata)
Among the many oddities in NieR: Automata's story, the entire first two playthroughs of the game are little more than its prologue. Throughout the first two playthroughs, the story follows Androids 9s and 2B, almost always together as they battle the Machines.
Following their victory, Automata's third playthrough focuses on a new story as the two launch a follow-up attack. When things go wrong, 2B has to be mercy-killed by new-player character A2. 9S swears revenge on A2 for this. The rest of Automata follows their separate journeys, with the player now forced to control lone androids rather than having an AI helper.
4 The Warden Is Alone In The Fade (Dragon Age: Origins)
Most of Dragon Age: Origins is spent with a versatile and capable party. The party cover the skills and combat that the Warden, the game's main character, is less-than-capable in. The party mechanics are a huge part of the game, and each of its members are major players in its story.
As such, it is a big change when the main story quest, The Fade: Lost In Dreams, has the Warden wake up alone in the magical realm known as the Fade. A major part of the quest is freeing their party members from their own forced dreams in the Fade, to weaken the Sloth Demon that has them trapped.
3 Your Party Is Stolen By An Imposter (Paper Mario: The Thousand Year Door)
Companions make up a major part of Paper Mario: The Thousand Year Door, able to help Mario explore the game's world and battling enemies alongside him. When Mario is alone, the player is on the back foot in combat and in exploration, denied a wide range of useful support abilities.
In Paper Mario's fourth chapter, Creepy Steeple, Doopliss uses his powers to impersonate Mario. Easily fooled, Mario's companions all abandon him, leaving Mario without his name, appearance, or party. It is the last that often bugs players - until Mario acquires a new party member in Vivian, the game's combat is far more brutal.
2 Ike And The Black Knight Fight One-On-One (Fire Emblem: Radiant Dawn)
The parties in the Fire Emblem series often reach as large as twelve (or more) members in a single battle, owing to the game's nature as a turn-based tactics RPG. In the Fire Emblem: Radiant Dawn chapter Rebirth 2, Ike and the Black Knight engage in a second duel, this time with a magical barrier separating Ike from his party.
Although the player continues to control the rest of the characters, they are engaged in a separate battle and largely unable to help Ike. By this point in the game, however, Ike is powerful enough that the battle is usually over quickly.
1 The Party Are Scatted In The Fortress Of Regrets (Planescape: Torment)
The final dungeon of acclaimed Dungeons & Dragons computer RPG, Planescape: Torment, takes place in the aptly-named Fortress of Regrets. This fortress is the residence of Torment's main villain, the Transcendent One. Upon arriving in the Fortress, the party are scattered across it, separated from one another.
Although the Nameless One has his share of problems, his party suffer more. As the player battles through the Fortress, their other party members are confronted one-by-one by the Transcendent One. Nearly all of them die fighting him. By the time the Nameless One reaches the final boss, almost none of his party remain alive, let alone fighting alongside him.