Iron Man Guide
I did this one 4 times before this trophy appeared, so this seemed harder than it actually was. Turns out I used Tim for the previous runs (he makes levels like 3-19X easier), which voided the trophy. Overall, I think how long it will take you to get this trophy will depend on how well you know how to manipulate the homing missiles that are scattered throughout this world.
My Recommended Order
17, 19, 6, 8, 9, 10, 12, 18, 16, 20, 2, 13, everything else (that's 1, 3, 4, 5, 7, 11, 14, 15)
(Use The Kid unless I say otherwise)
All level ratings are relative to this world's levels only.
Do a long double jump over the two gears. Rest of the level is easy if you take your time.
I don't recommend holding the run button for most of the level except for the part where you need to jump between two gears. The rest of the level isn't too bad. Don't underestimate it however, as the tiny walls can make it easy to screw up.
Hold the run button the whole way. You can easily double jump past everything except the part where you need to jump between two gears. For that, do one jump and you'll be able to pass it at the peak of your jump. Use your other jump to compensate if you think you won't make it. The return trip is pretty much the same process.
3-4X (Use Meat Boy)
All the gear shooters fire straight down for this level, so they should be easy to dodge. Take it slow and stay in the air a lot so the conveyor belts don't control your motion too much. After getting the key, drop at normal walking speed to the right and you should make it to Bandage Girl (tap the run button a bit just to be safe).
Double jump FTW. With it, you don't have to go anywhere near the gears to clear the level.
You need to jump off the top of the 4th conveyor belt while holding the run button to reach the 5th one, which can be tricky to get used to. And you need to do it twice. You can use Alien Hominid (assuming he doesn't void these trophies) for an easier time, but The Kid gets the job done decently, too. When dropping down , stay near the yellow windows and you'll be safe.
The double jump and exit to the map trick make this level really easy to not die in. Getting the timing for the first couple keys can take a while though. Start by running, grabbing the first key, and double jumping over the pit to get the 2nd key as it falls. After that, you just need to ride the 2nd conveyor belt and do a running double jump at the peak to get the last key to unlock the way to Bandage Girl.
Hold run and keep moving until you reach the top of the building. Once on top, head left and wait a little bit for the launcher above you to fire, then jump up the wall. From there, keep running left and jump once to dodge a missile from the left launcher. You should be able to reach Bandage Girl from there.
This one takes a few tries to get used to, but it's not too bad overall. You can pick the left or right wall if you want (experiment to find out which works better for you, I use the conveyor route, personally). Once you're above the missile launcher, the rest of the level isn't too hard. Just keep running to get the key and dodge the missile launcher guarding it, then go back and double jump all the way to Bandage Girl.
3-10X (Use Meat Boy)
This level is all about controlling where the missiles fire. I recommend waiting after a launcher fires before crumbling the blocks and dropping down the lower areas.
On the way back up, stand a few spaces away from the corner, wait for the launcher above you to fire, then jump up after it does. Repeat until you reach the very top.
Simply head to the first wall, double jump to the top (or use Alien Hominid), then jump over the gears and head left to Bandage Girl.
Pretty annoying level, but doable once you get the launcher's timing down. The trick is to stay left, and jump in the air just as the launcher is about to fire, then jump again when it fires to dodge the missiles. When you get past the part with a salt wall and a gear, do a long jump to get the key, then do another jump as soon as the launcher fires. Rest is pretty much the same dodging process.
3-13X (Use Meat Boy)
The hardest part of the level is the part at the very bottom where you need to cross between two of the big gears. Using Meat Boy to run through it will make this easier. The Kid has less room for error, but he has an easier time navigating the rest of the level.
Double jumping makes this level a lot easier. Not really much to say here.
Just stay right and double jump your way to the top. And don't touch any of the gears on the moving platforms.
When you get inside the chamber, jump while sliding down the wall to clear the gear inside. Grab the key, then go back through the chamber, and hang out on its left wall. Once the wall of gears starts moving right again, do a long jump over them, then do a double jump to close the gap between you and Bandage Girl.
3-17X (Use Meat Boy)
We don't get Captain Viridian on this version, making this level very annoying. I highly suggest doing this one first because it's so easy to screw up a jump and get nailed by a missile. Use Meat Boy since he's the fastest and requires less jumping to clear the level.
Once you know what to do, this level's difficulty drops to at least Easy-Medium. Start by jumping over the first two gears, then run right and jump over the 6th and 7th set of gears (both should be travelling on the ground). Around the 4 second mark, you can jump to the wall and grab the key without worrying about dying to a gear. From there, head back left and just hang around the wall until the locks are all gone and the way to Bandage Girl is open.
3-19X (Use Meat Boy)
Getting down is the hardest part. Start moving right to dodge a missile, and jump into the hole to the right. Try to stay as left as you can without touching the block. Once you descend to the middle level, jump over a missile and enter the nearest hole and repeat what you did with the previous one. From there, you'll need to crumble the blocks on the left while jumping occasionally to dodge missiles.
Once the way to the conveyor belt is clear, get on the conveyor belt, and press and hold the jump button when you're getting close to the bottom of the first gear in the way. You'll end up jumping and sliding high enough that you can just jump to the 3rd conveyor belt and ascend to the goal.
A fairly lengthy level. Take the conveyor belt to the building. Wait a bit at the entrance for the missile launcher to fire before you jump up. When on top, stay at the corner and jump when the launcher fires again. The blocks will crumble allowing you to jump to the upper level. The launcher to the left will keep firing missiles at you. When the missile is closing in on you, jump to the wall and make sure to touch all of it. The wall will crumble and you can move on. Repeat this until you get to the last section.
The last part is all about being on the move and manipulating the missile launcher. Once you get the key, you can stand on the platform right of the launcher and just play hopscotch with the missiles while you wait for the locks to disappear.