Okay, look...
The last stage is a boss stage (you have to battle all bosses).
The first 4 bosses are easy, because you battled them already in the 4 zones which you played before. But the 5th one is pretty hard...I needed 3:30 minutes for the first 4 bosses. But 6 minutes have passed (total time : 9:30), i injured him a lot! And he wasn`t still down >.<
After ever injuring, he/it gets harder to beat!