LEGO Batman

To max out the stud counter, you need to have 4 billion studs. In your wallet, ie not a cumulative total.

Multiplier cheats DO NOT disable achievements. So you can get a hold of all the multiplier cheats and then put them all on, and you can get a "x3168" multiplier and you can walk out of most levels with at least a few hundred milion,

If you are a purist though, just play your favourite levels over and over....alot. Or you can find the Red Blocks from the first 5 villain levels. They unlock the multipliers for purchase also.

z0rrofox made it pretty clear what to do here, and this is probably the most logical method since getting that many would be way to time consuming. I would like to contribute to the solution above with some cheats for score multipliers.

Score x2 Multiplier N4NR3E
Score x4 Multiplier CX9MAT
Score x6 Multiplier MLVNF2
Score x8 Multiplier WCCDB9
Score x10 Multiplier 18HW07

(thanks to cheatcc.com)

You need to have 4 billion Lego studs at once. Given that:

Silver stud: 10
Gold stud: 100
Blue stud: 1,000
Purple stud: 10,000

This will be painful to do without the x2, x4, x6, x8. and x10 multipliers on, *all at once*, for a total multiplier of x3840. If you want to do this the "right" way, you can unlock these multipliers by finding the red Lego brick in each of the five levels of the first Villain episode, and then purchasing each of the multipliers as Extras. All told, the five multipliers will cost 15 million studs.

Alternatively, you can use the "Enter Code" feature of the game to unlock the multipliers early:

x2: N4NR3E
x4: CX9MAT
x6: MLVNF2
x8: WCCDB9
x10: 18HW07

Just make sure to turn on all of the multipliers in the Extras menu. After doing so, you should see a magenta-colored x3840 in the upper-left part of the screen. Extras reset every time that you load your game, so make sure to repeat this step after loading.

Other than that, just play through anywhere from about 7-20 complete levels with the x3840 multiplier in effect. (I got about 600 million studs going through Hero level 1-5 in Free Play.) Make sure to destroy as many objects and complete as many build-its as you can. Free Play works best, because you'll be able to switch characters and suits on demand to access more areas and therefore more studs.

Places to find lots of studs:

1. Multipliers count while in the Batcave and Arkham, too. With the x3840 multiplier in effect, a character with double jump (Clayface, Poison Ivy, Harley Quinn) can earn almost 100 million studs in the Arkham mission room. The Batcave and Arkham studs regenerate after reloading the game and when returning to the Batcave/Arkham from playing a level.

2. Machines for the Attract Suit sometimes cough up a lot of blue studs if you feed them a *second* set of 25 pieces. Usually, it is possible to gather that many pieces only in Free Play.

3. Completing a minikit by finding all 10 pieces of memorabilia in a level will earn you a lot of blue studs.

I just came across this by accident,
have all you multipliers on and have Mr. Freeze's Iceberg
go into
Hero Side -
Episode 2: Power Crazed Penguin
Batboat Battle

use the freeze ray on the penguin sub that can only be destroyed by the purple torpedo and keep freezing it, the studs just keep coming!

To max the stud counter out, get 4 billion studs.

Enter the x2 x4 x6 x8 and x10 so it becomes x3840 and you can get over 400,000 studs total. Or,in the first villain episode (The Riddler's Revenge) all five score multipliers are there. Collect each red power brick in the five levels and then purchase them at the computer in the Batcave or the Arkham Asylum. Over time you will get this achievement.

VERY FAST or UNATTENDED

1) VERY FAST: Arkham Asylum (base) > right corridor
Active Bricks: Character Studs
Optional Bricks: Multipliers (faster) - you can add these as you go

Go back and forth here beating up thugs and collecting their studs. Each time you can afford a new multiplier, go back to the middle and buy it. Takes about 30 mins (with no initial multiplier bought).

Seems to work faster than other methods because you get an additional multiplier that builds with consecutive hits - you'll regularly get a 10x for this. Recommend using a character without a gun (e.g. Poison Ivy) since its the hand to hand fighting that builds the multiplier.

2) UNATTENDED: Hero 2.2 - Batboat Battle > 2nd last area
Active Bricks: Character Studs, Stud Magnet
Optional Bricks: Invincibility (easier), Multipliers (faster)

There are two penguins dropping mines. After a while they explode on their own giving studs! You should be able to safely sit 2 screens away and just leave them to it!

Note: I believe I did it without invincibility but I might be wrong. Comments suggest you need this.

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Please leave a comment if you vote negative or have more info so I can improve the solution