Not saving Odin probably wasn't the greatest idea...
- Mephisto's Realm, oh dear god Mephisto's Realm. Not only is the level basically an Expy of Hell, but throughout the entire level you're pitted up against all kinds of demons that do things like swapping bodies with your character or trying to eat your character. Additionally, the level has a beyond-horrifying soundtrack that contains the sounds of thousands of trapped souls either moaning or screaming in ever-lasting torment. Sweet dreams.
- The cinematic that details what Doom did with Odin's powers while the playable heroes are away, showing him blowing up some ICMB, then turning around to see the heroes who rose up to try to stop Doom, including a heavily-mutilated Colossus covered in dents and missing a hand and part of one of his legs, and the Hulk, Professor Xavier, Magneto, Shadowcat, White Queen, and Gambit laying on the ground either unconscious or even dead. Cyclops rises up and fires an optic blast, only for Doom to block it and push it back at him. But when Colossus makes an attempt to stop him and spits in his face, Doom throws him around and then corrupts him before doing the same to the others.
- To make matters worse, Doom's control of Odin's power is unstable, making tears across time and space with each use, and it was mentioned if he wasn't stopped everyone and everything would die.
Hank Pym: If the tear becomes large enough, there's no force in the universe that can stop it - even Doom's powers. The rip will continue to grow until it envelopes everything and chaos reigns. Our universe will become a lifeless, useless void.
- Several of the possible "bad endings" you can get depending on the choices you make.
- If you don't save the Omega Base Computer, the Legacy Virus will run rampant across the Earth and doom the mutant race to extinction.
- If you failed to heal Namor, he dies and Krang will assume his throne and wage war on humanity with the nuclear weapons he and his army gained after taking out a warship.
- If you fail to save Senator Kelly in Murderworld, he eventually escapes and successfully sponsors a government bill that forces all mutants into re-education camps to brutally enforce mutants to never use their powers.
- Should you neglect to look for Valyrie's sword, Valkyrie and Balder will be killed in battle. Thus Asgard will deny a century of contact with Earth.
- Should you ignore Volla's ring, she will not warn Odin of an attempt on his life. His assassination would plunge Asgard into chaos and soon, Thor will become king but Sif will be killed in the fighting.
- If you didn't save Lilandra, the Shi'ar will refuse to aid Earth in destroying an incoming asteroid, resulting in the obliteration of the entire west coast.
- The Morton's Fork scenario in Mephisto's Realm where you can either save Jean Grey or Nightcrawler from death and the consequences of both choices. If you save Nightcrawler, then Jean will come back as the Dark Phoenix and enact destructive vengeance upon those who didn't save her. If you save Jean Grey, then Mystique will lethally brutalize Charles Xavier out of revenge and cause the whole team to disband out of grief forever.
- If you didn't find the Ultimate Nullifier, Mephisto will attack the Earth, and without the aid of said weapon, he will cause a tremendous amount of destruction before finally being defeated when the Alliance comes back together.
- In perhaps the worst ending of them all, failing to free Odin leads to him later refusing to help Thor fight off an invading Thanos. As a result, Thor and the other heroes are killed in battle as Thanos takes over the Earth and continues to rule it for centuries. The unpleasant image that accompanies the ending shows that he's reduced Earth to ruins and keeps Captain America's smashed shield, Thor's hammer, and a still-alive Invisible Woman as trophies.
- Mephisto's bad ending ends with him making a very unpleasant Nightmare Face at the viewer...
- Galactus swearing to destroy the Earth after the heroes steal a device from him required to defeat Doom. The heroes could only slow him down before and now he's officially gunning for the destruction of Earth!
- Whatever Odin has in store for Loki and Doom after regaining his powers was flat out described to be A Fate Worse Than Death and it's never shown what he does to them but it is known they're still being tormented during the game sequel.
Marvel Ultimate Alliance II
- In the second game the Pro-Registration side is using Mind Control to control villains and force them to hunt heroes for them. During one of the missions you can find a audio clip of Reed Richards casually explaining the device to what's presumably a room full of young scientists, while the
victims villains, who actually volunteered to join their side (albeit presumably for selfish reasons), fruitlessly scream in terror while they're forcibly injected with mind suppressing nanites and their minds are subjugated in the background. It's somewhat more terrifying than it sounds. Later, the playable villain characters talk hatefully about how it felt to lose their minds and individuality to the Fold and agree to join, no-strings attached, if only to make sure that that sort of thing can never happen to them again. It takes a lot to make Reed Richards the most terrifying character in a game that includes characters like Venom and the Green Goblin, who you instead feel sorry for, but there you go.
- Venom's breathing slowing as he's sedated, from that same recording. And 10 seconds later when an unidentified female villain is brought in to be injected, all the while screaming for the S.H.I.E.L.D. personnel: "No! Get away from me! No!"
- The fact that Reed Richards reverse engineered that tech from something a known supervillain made and Iron Man and SHIELD agreed to use it without even thinking twice, all in the name of the greater good. And none of them get any sort of punishment for it.
- Just.... Everything about Penance. Just seeing what was once known as the Fun Personified superhero Speedball become a self-mutilating Combat Sadomasochist that spews blue fire out of guilt over the Stamford Incident is horrifying to see. Not to mention his personal audio logs.
- One of Venom's attacks, Leaping Feast, has him lunge at an opponent and start eating them, replenishing health. Imagine what this looks like from his enemies' perspective.