The other solutions are great but this solution will guide you through every step to unlocking this achievement.
To unlock this achievement, you need to unlock each character’s four outfits with the exception of Moon Knight, who only has three. DLC characters are not needed but do have their own outfit-related achievement.
There are also a few characters you’ll need to unlock throughout the game before you can start working on getting their outfits. These characters are:
Doctor Strange - unlocked after helping him in Mandarin’s Palace.
Blade - unlocked by using the claw game in Murderworld.
Ghost Rider - unlocked by rescuing him in Mephisto’s Realm.
Nick Fury - unlocked after defeating Dr. Doom.
Daredevil - unlocked by collecting 5 of the 11 respective action figures.
Black Panther - unlocked by collecting 5 of the 12 respective action figures.
Silver Surfer - unlocked by getting at least a bronze on all 34 Comic Missions.
The second and third outfits are unlocked by getting 175 kills with the respective character, while the fourth is gained by earning a bronze on their Comic Mission (these are unlocked by finding Simulator Discs throughout the game). So while making your way through the game, be sure to switch character after you’ve reached 175 kills. I’d suggest playing through the game on normal as you need to beat that difficulty to unlock hard.
Onto the steps to getting the achievement (this will be outlined in the order the steps first become available while making your way though the game).
Daredevil figure 1/5 - while escorting Dum Dum Dugan, you’ll reach a large room where he’ll inform you you need to disable the primary drive train (text pop-up will appear). After walking down the stairs, proceed down another set of stairs to your right where you’ll find the action figure waiting for you.
Captain America Simulator Disc 1/29 - after leaving the large previous room you’ll have another brief conversation with Dugan. Go through the door on your right and immediately to the right will be the Sim Disc.
Wolverine Simulator Disc 2/29 - after clearing out the enemies and talking with Bruce Banner about the damaged shutoff, go through the previously shut door. Open the first door to your right and the Sim Disc will be in front of you.
Black Panther figure 1/5 - after dropping the object onto the glass to break it, proceed inside. Sitting by the railing to the left of the door in front of you will be the action figure.
Iron Man Lab (Entrance is the waterfall near the save station in Stark Tower.)
Black Panther figure 2/5 - go down the stairs directly in front of you and underneath these stairs is the action figure.
Iron Man Lab
Iron Man Simulator Disc 3/29 - from the entrance, go down the stairs, continue straight forward and you’ll find the Sim Disc sitting on a desk to the right of Iron Man’s suit.
Black Panther figure 3/5 - after entering, walk straight to the side opposite the entrance and you’ll find the action figure sitting to the right of a large pipe.
Temple of Negrete (Entrance opens up behind you after talking to Namorita.)
Mr. Fantastic Simulator Disc 4/29 - to the right of the clam you have to force open is a breakable wall. Break the wall and you’ll find the Sim Disc.
Daredevil figure 2/5 - you’ll reach a large area with a save point and two objectives you need to destroy. Follow the left wall of this area and you’ll find the entrance to Atlantean Throne. With your back to this entrance, proceed forward. After swimming between two columns you’ll come across a clam to force open. Opening this will grant you access to a nearby chest. Swim to the middle of this large area to find the chest (it has a green arrow above it). Inside this chest will be the action figure.
Thing Simulator Disc 5/29 - you’ll eventually come to a large room with spinning blades at the bottom of a staircase. When looking at this staircase, you should see a red X on the left of your minimap. Go up these stairs and follow the balcony to your right to find a door. Inside this room will be the Sim Disc.
Daredevil figure 3/5 - after exiting the previous large room and proceeding through a room filled with spinning blades you’ll end up on a balcony overlooking yet another large room. Jump down and to the left of the two columns directly in front of you will be the action figure.
Crimson Dynamo Simulator Disc 6/29 - shortly after helping Doctor Strange, you’ll come across three spinning blades surrounding this Sim Disc.
Black Panther figure 4/5 - right before the entrance to Mandarin’s Court, there will be two large Buddha-like statues. Destroy the statue that’s to your left when facing the entrance. Go through the two now unblocked doorways to find the action figure.
If you haven’t already unlocked the achievement for defeating Mandarin, make sure you return to the previous save station and save before entering Mandarin’s Court. Doing this will prevent Doctor Strange from locking as a playable character.
Sanctuary (The entrance is the spiral staircase you see when you first enter the Inner Sanctum.)
Doctor Strange Simulator Disc 7/29 - from the entrance, turn right and head up the stairs. The Sim Disc is up here atop an opened book.
Daredevil figure 4/5 - go up the other set of stairs the would be to your left when you enter. The action figure is at the end of this walkway.
Make sure to save before leaving to Dr. Doom’s Castle. When you first get to Castle Doom, rush past all the enemies to the last Daredevil figure. You’re going to be reloading your last save after collecting it so there’s no need to kill any enemies.
Daredevil figure 5/5 (Daredevil Simulator Disc 8/29) - after passing through the hallway with the moving gates, you’ll come to a large room. Go down the stairs to your right and continue up the next set of stairs to your right. You’ll see two wooden gates, ignore the one directly in front of you and destroy the one to the left. In this small room, destroy the four barrels and the action figure will be to the right.
After getting the achievement for unlocking Daredevil, load your last save and recollect the last action figure. This time you can proceed as normal and kill all the enemies.
Mysterio Simulator Disc 9/29 - from the entrance to this same large room (after passing through the hallway with the moving gates), now go down the stairs to your left and continue up the stairs to your left. Destroy the wooden gate directly in front of you and in this room will be the Sim Disc.
Luke Cage Simulator Disc 10/29 - as soon as you enter Big Top, the Sim Disc will be to your left.
Blade - take the right path and continue forward until you come across a tent to your right. Inside this tent will be a hammer, take it. Exit the tent and head right where you’ll see a blue X to use the hammer. Charge up the hammer with B to hit the X and open the gate.
Continue in this area and after passing an open purple/white striped tent to your right, proceed forward to find the Claw Challenge. Simply complete the QTE and Blade will unlock as a playable character.
Maze-O-Death (After unlocking Blade, turn around and head to the left of the open tent. You’ll see another open tent, enter this tent. Proceed to the back of the tent to find the entrance to this area.)
Elektra Simulator Disc 11/29 - proceed through the maze, pulling the fingers as you come across them to access the subsequent areas. To the left of the fourth finger, you’ll see the Sim Disc.
Be sure to save your game before entering Fun House to prevent Blade from becoming locked as a playable character, as you’ll be reloading again after collecting the next action figure.
Black Panther figure 5/5 (Black Panther Simulator Disc 12/29) - shortly after entering you’ll come across three doors. Take door number 3 and follow the path. At the end of this path, in a large room, sitting in front of three toxic blowers will be the action figure.
After getting Black Panther’s achievement, reload your save and recollect the last action figure. Then return to the save point and save again.
Blade Simulator Disc 13/29 - from where you first spawn in, turn right and continue in that direction. You’ll see the Sim Disc on a plate with three vases.
Scorpion Simulator Disc 14/29 - shortly after entering this area you’ll cross a bridge. Follow the path and you’ll see the Sim Disc in a room to your left.
After collecting this, make sure to save at the save point next to the entrance of this area. If you haven’t already unlocked the achievement for defeating Mephisto, the character you chose to take Ghost Rider’s place will remain locked. After defeating Mephisto and earning that achievement, reload your save and proceed to defeat him again. After defeating him for the second time, you will then have access to the previously locked character.
Ghost Rider Simulator Disc 15/29 - from where you first enter, head left and you’ll see the Sim Disc on a small island.
Storm Simulator Disc 16/29 - as soon as you enter, you’ll see the Sim Disc to the left.
Spider-Man Simulator Disc 17/29 - as soon as you enter, head left when you can and you’ll see the Sim Disc near the edge of the walkway.
Warriors’ Hall (In Courtyard of the Gods, looking at the statue in the middle from the save point, turn around and head towards the yellow exclamation mark on your minimap. Talk to the Viking Warrior to gain entrance.)
Thor Simulator Disc 18/29 - from the entrance, go straight forward then look to the left of the campfire you come across. Up some steps in an alcove will be the Sim Disc.
The Great Forge
Invisible Woman Simulator Disc 19/29 - after passing through the first room, go to the stairs on the left side of the large lava pit and into this other room. Proceed down the stairs to your left and after passing the second set of stairs you’ll find the Sim Disc.
Deadpool Simulator Disc 20/29 - after freeing Heimdall, talk to him and agree to locate his horn. Now return to the previous room and a door will open up. Enter this newly opened area and after reaching the room with the brief cutscene showing Heimdall’s horn, the Sim Disc will be to your left.
Shore of Corpses
Shocker Simulator Disc 21/29 - at the end of this area, you’ll go up a small slope and to your left will be a save point. Turn right to find the Sim Disc.
Spider-Woman Simulator Disc 22/29 - shortly after entering this area you’ll come to a bridge. While crossing this bridge you should see the Sim Disc off to the left.
Iceman Simulator Disc 23/29 - at the end of the large room you start in, you’ll have to move some boxes out of your way to proceed. Go up the now unblocked stairway and head right. Head up the next set of stairs and through a door leading to another large room.
Go down the stairs in front of you and then the stairs to your left. Go straight forward to the opposite side of the room and up another set of stairs. Then left up the final set of stairs where you’ll find the Sim Disc waiting.
Ultron Simulator Disc 24/29 - shortly after entering you’ll come across a door that needs to be opened with two keycards that enemies will run off with. Follow the enemy who ran right and you’ll eventually come to a large blue beam and the option to go left or right. Head to the right and you’ll come across the Sim Disc.
Ulik Simulator Disc 25/29 - shortly after entering and meeting two mini bosses, you’ll have a red X on your minimap. Standing at that X, head as for north (north being the top of your screen) as you can. Once you hit the wall, jump up to the higher ground to your right.
Continue right along the north wall until you’re atop a glass floor (you should be able to see the Sim Disc in the area below you at this point). Break the glass and the Sim Disc is near the northern right corner of this area.
Piledriver Simulator Disc 26/29 - after crossing through the first room and onto another bridge, Nick Fury will inform you that you’re near some Magnetic Shield Generators. After destroying one of them, proceed through the now unblocked doorway and at the end of the hall in front of you will be the Sim Disc.
Ms. Marvel Simulator Disc 27/29 - after entering, follow the only way forward and you’ll come across the Sim Disc before heading left again.
Human Torch Simulator Disc 28/29 - immediately after the dialogue with Galactus, head to the left at the fork and you’ll find the Sim Disc.
Heights of Progress
Dragonman Simulator Disc 29/29 - go straight forward from where you enter and very quickly you’ll run into this Sim Disc.
Now that you’ve collected all of the Sim Discs, all you have left to do is unlock Nick Fury as a playable character, earn at least a bronze on all Comic Missions (I’ll tell you how to actually access these in a bit), and grind out your remaining kills.
Be sure to save at the nearby save point before entering the green portal to Doom’s Throne. If you haven’t already unlocked the achievement for defeating Dr. Doom, there’s a chance you’ll have to defeat him twice to actually be able to access Nick Fury as a playable character.
Once you’ve defeated Doom and earned the respective achievements, check to see if you can choose Nick Fury when changing your team. If you can, you’re good to go so save again. If you can’t, you’ll have to reload your previous save and defeat Doom again.
Now get to the nearest save point and extract to Stark Tower (Act 1). With your back to Iron Man Lab, go up the stairs to your left to find the Training Simulator. This is where you can access all the Sim Discs you’ve been collecting. Now go through them all getting at least a bronze, saving after each successful attempt.
Make sure to save before the last one and after unlocking the achievement for Silver Surfer, reload your save and complete the last one again. Now you have access to all playable characters and have all characters’ fourth outfit.
Only thing left to do is grind any remaining kills. A good way to quickly grind kills is load up any Vs Comic Mission that takes place on Asgard (the first being Crimson Dynamo). Then just kill the infinitely respawning enemies until the time runs out. Once you’ve finished getting 175 kills with your last character, the achievement will unlock.