The Bigger They Are...

A Fallout 3 Xbox 360 Achievement. Earned by killing all 5 Super Mutant Behemoths in the game.

SMB 1: Galaxy News Radio
Everyone should encounter this one during the Following in his Footsteps quest. Although, this one is the best because all you have to do is shoot it once and you get the experience and the credit of killing it. Also you get the help of the Brotherhood of Steel.

SMB 2: The Capital Building
For this one, you have to battle your way threw many Super Mutants and finally, you will get to a room where a bunch of Talons battling the Super Mutant Behemoth. Tip- Don't go melee. Not just melee weapons, don't go near it. This one will attack just you if you get anywhere near it and ignore the others. Also, there are two or three Super Mutant Brutes up on the risers, yet they don't attack you as much.

SMB 3: Evergreen Mills
This one is by far the easiest to kill. Because it's in an electric cage! Thats right, deep within the dead bodies of the local Raiders in sunny Evergreen Mills is a caged Behemoth. There's only one way to open it, and that's to destroy the eletrical box to the left, but why would you? You can shoot at it from the outside with any gun and it won't do anything.

SMB 4: Jury Street Metro Station
Well, it's not exactly in the Jury Metro, but you just go straight West and past a red building. Keep going and you should come by a little cliff. Go down and there should be a little Super Mutant area on train tracks. Just kill them all and go up to the tipped over big red box there should be some open-able carts. Open the one with the teddy bear. Now, this may seem weird, but you must pick up the teddy bear, wait a couple of seconds, then turn around. On the top of the hill, there should spawn the 4th Super Mutant Behemoth. Kill him however you like.

SMB 5: Takoma Industrial
Go to the right and there should be an open area, but covered with Super Mutants. There are two ways to kill this one. You can either...
 * 1) 1- Kill it with your weapons
 * 2) 2- *RECOMMENDED* On top of a bus, there should be a button around some First Aid Kits and a dead Mercenary. Activate it, and a series of nukes should fall in random locations threw out the area. Saves health and ammo.

Hope this guide helps!