At the start of this level are some mines. If you walk over them, they'll explode and hurt you. But you can also harm the Mad Gears with them, so try to lure them over the mines as much as possible. The opening section has several of you basic punks, plus a couple of Elicks. Once they've been defeated, you'll have to fight Leon, Robert and Grandpa Andore.
Move on to find 6 mines on the ground, 3 on either side. Move to the upper middle and wait, you can usually get several enemies from the left to walk over the mines. Once they're defeated, Andore, Andore Jr and Atlas will walk on from the right, so make use of the remaining mines to do some big damage to them. Defeat them and then head right, where you'll see the entrance to a building. There are another 3 mines to make use of outside the door.
Try and save at least one of the mines for Andore, as he'll appear here, along with a lot more Mad Gears. Once they're dealt with, head into the building. Robert and Atlas will show up first, take them out and then deal with the weaker underlings who come on. There's also a box to break open here if you want to try and get an item. Once the enemies have been defeated, an elevator platform comes down, which will take you up a floor.
Once you get off the elevator, Grandpa Andore, Robert and Elick will appear. Defeat any two of these and two more Elicks will walk on. Defeat them all and go right, where some weaker enemies are waiting, along with a barrel. Head on to fight some more powerful guys, including Leon, Robert and Andore Jr. When one of these is defeated, Elick will come on, so be ready to take him out too.
You'll then head back outside. Defeat Mic and Schot, and break open the barrel to hopefully get a health item. Move on and you'll face Elick, Elias and Andore Jr. When you defeat one of these, a regular Andore will come on. Defeat everyone and move further on, the first enemy to watch out for here is Eliot, who has a lot of health.
More enemies will come on, including Robert and Atlas. Defeat them and move on to find two barrels, don't destroy them yet. Grandpa Andore will come on, and he has a lot of health. By not destroying the barrels, this will prevent any more Mad Gears from coming on, so defeat Grandpa Andore first. Once he's gone, break the barrels, this will let a couple of Elicks and Andore Jr come on.
Once they've been dealt with, you'll drop down below. Take out the basic Mad Gears, which will let some stronger guys to come on, including Eliot. Watch out for Joe, he and a clone will run on and throw molotov cocktails. The last enemy to come on will be Andore.
Head on right to find Bratken. He'll burst out of his cell, and make his way towards you. He's quite slow, but he has a jump kick attack which can cover a decent amount of distance. Bratken receives plenty of backup from other Mad Gear members, including Joe.
Bratken's jump kick is his main attack, but you can hit him out of the air with a jump kick. His other attacks include a charge, a punch, and a kick, but he only tends to use any of these when he's close to you. Throw him, then move above or below him, then go for another grab. It takes a while to defeat him since he has a lot of health, but it's the easiest way to win.