The first lot of enemies you'll encounter are Mic, Bull and Elick. Even the basic Mad Gears get high amounts of health now, so be prepared for some long fights. Another Elick will come on, along with Leon and Andore. Defeat them and move all the way to the right, where you'll see a wall. There's a box to break here, and you'll face Atlas, Eliot and Leon.
Once they've been defeated, Leon, Robert and Jony will come on. There is then Atlas and another Jony to deal with, once they're defeated, you'll automatically jump down.
You'll land on a boat. Head right and you'll see a door, but then Jack, Elijah and Mark will come on from the left. They may be the lowest of the Mad Gears, but they've got a lot of health. Defeat them and then be ready to fight Eliot, Leon and Andore Jr. Once they're beaten, your character will destroy the door.
When you get to the next section, Leon and two Roberts will appear. They tend to jump at you right away, so be ready with a jump attack to take them out of the air. As you defeat these guys, more of them will come on, so watch out for jumping attacks. Move on and you'll come up to another door. Before you can go through, Andore, Mark and Mic will come on from the left. Defeat them (they don't have much health), and then several Elicks will come on. Watch out for their charge attacks.
After breaking down the door, you'll jump off the boat automatically, and jump over onto a drawbridge. You'll then enter an elevator, which will start to move up. There is a health item here, but you might want to try and save it for later. Mad Gears will start dropping down from above, and there's not much space to fight here. Keep throwing enemies around.
The enemies who come on will get stronger and stronger, which includes the return of Grandpa Andore. Defeat them and the elevator will come to a stop at the top floor. You'll smash down the door and head out to meet the boss: Rolento.
Rolento's main strength is his speed, as he can move around incredibly quickly. He tends to rush in to try and strike you with his staff, and he can also do the off the wall jump kick, just like Maki can. He also tends to jump onto the balcony (where you can't hit him) and then jump off to do his jump kick from there. One way to wear him down is waiting at either side of the screen, then let him move towards you. As he does, do a neutral jump kick, then keep repeating this strategy.
Try not to let Rolento get too close to you, as he has a throw. Another strategy is to let him jump onto the balcony, then when he jumps off, move around to avoid his jump kick. As he lands, you can grab him and do a throw on him. Once he's taken enough damage, he'll change tactics. He'll start throwing grenades at you, and he throws out several at a time.
He also tends to jump on the balcony, throw several grenades down, then jump off. What you need to try and do is hit him as he lands, but keep a careful eye on were the grenades are, as these do a lot of damage if you get caught in the explosion.