- Estimated achievement difficulty: 4/10
- Solo Only (Offline): 2 
- Solo or Co-Op (Online or Offline): 56 
- Approximate time to 1250 leeching Hard save: 20-25 hours
- Approximate time to 1250 doing Hard yourself: 30-35 hours
- Minimum number of playthroughs needed: 2
- Missable achievements: Yes
- Does difficulty affect achievements: Yes
- Unobtainable/glitched achievements: No
- Extra equipment needed?: No, but extra controllers speeds up a few achievements
UNLEASH THE GREATEST SUPER HERO ALLIANCE EVER. Marvel: Ultimate Alliance lets players create their ultimate team from the largest superhero alliance ever as they engage in an epic quest to determine the fate of the Marvel universe. Players can create and control their own completely unique team, selecting from the largest roster of legendary superheroes ever assembled in one game, including Spiderman, Wolverine, Captain America, Ironman, and The Thing. Through the epic campaign, the heroes will battle, team-up, and interact with over 140 characters from the Marvel universe and ultimately confront notorious villains such as Dr. Doom, Galactus and The Masters of Evil.
Step 1a: Normal Playthrough
If you don't know someone or don't think you'll be able to find someone who has beaten the game on Hard to help you get the Excelsior achievement, you'll need to start your game on Normal to be able to unlock Hard at the end. If you will have help for that, feel free to play on Easy instead (Step 1b), but read this step for tips on the story mode.
During this playthrough you will want to make sure you use this collectible guide to find all the action figures and simulator discs. You can ignore any of the stat upgrades and sketch books if you want, they are not used to unlock anything achievement-related, but some of the sim discs are missable, so be careful about getting those as soon as you can. Also be sure to switch characters whenever you get 175 kills (or 250 if using a DLC character) so that you can gradually work on unlocking all the costumes. This will save some time later.
Other things to work on: finishing moves (combos), throwing enemies off ledges, make sure you play the crane game in Murderworld to unlock Blade, check the DLC achievements for four missable achievements to ensure you have the proper characters at the right times, and do all the trivia questions.
Step 1b: Easy Playthrough
If you'll have someone helping you get the Excelsior achievement, there is no need to play on Normal, so begin on Easy and play through the game. Follow all the other suggestions in 1a though.
Step 2: Arcade Wins
Using a second controller or a friend, get the 100 arcade wins out of the way now. You'll want to do these now, as you'll get a ton of credits to unlock upgrades for your character, which will help in the next step.
Step 3: Simulator Golds
Now that you have a bunch of money to upgrade suits and character abilities, tackle all the simulations and get gold rank on each of them. During any of the missions where you can select your own team, be sure to select characters that you still need kills with and not ones with all their kill-related costumes already unlocked.
Step 4a: Hard Playthrough
If you do not know anyone with a Hard save, start a second playthrough now. You will be able to bring all your stats and unlocks over with you, though you'll want to make sure you've completed all the simulation disc challenges on a lower setting before doing this, otherwise they will ramp up in difficulty.
Step 4b: Hard Save Leech
If you have a friend or can find someone online who has beaten the game in Hard mode, you can quickly get the achievement for beating the game on Hard by having them invite you to their game and fighting Doom. Takes less than ten minutes.
Step 5: Unlock All Costumes
Likely the last thing you'll need to do is finish unlocking all the character costumes. Since you got Gold on all the sim missions already (if you followed this Road Map), you'll just need to rack up kills. Load up an Asgard sim mission with four characters who still need costumes, unlock them all by killing the infinite spawns, then finish the mission and start it again with a new set of characters.
[XBA would like to thank The Pants Party for this Roadmap]