Ratman is hiding in the sewer with his loyal rats and stinging flies. To defeat him, you have to get past them.
The procedure :
When you face ratman and his rats and flies, climb to the red wheel at the upper right, which will dump sludge on Ratman. Jump quickly between the rats. Then avoid his flies to jump over to him and cuff him.
It is not extremely difficult after some practice. The hardest parts, even when you know what to do, are the battles against Ratman's rats and against Crusher. (see related question)
There are three red wheels that lower and raise the water in the sewer. But the one you use in the Control Room is at the upper right, and you have to jump past three rats to reach it.
When fighting Ratman in the sewer chamber, you cannot stop the movement of the rats. You will need to adjust the timing of your jumps to avoid being hit.
Ratman is hiding in the sewer under City Park, with his pet rats and stinging flies.
if you mean the one in super power island then you need it for catching one of the crooks(one that lives with the rats)
there is only one girl and her power is super speed
You have to make a series of three jumps between the rats to reach the red wheel at the upper right (to dump the sludge on Ratman). Then evade the flies and jump from the middle raised pipe over to cuff Ratman.
You have to time your jumps between the moving rats, quickly going from pipe to pipe. You have to make a series of three jumps between the rats to reach the red wheel at the upper right (to dump the sludge on Ratman). Then evade the flies and jump from the big raised pipe over to cuff Ratman.
You use the flashlight which is found in the other world
Unlike the rats and flies, the roaches are just a crawly distraction in the subway before you fight with Speeding Spike. You can't affect them at all.
In the sewers on Super Power Island, Ratman is guarded by rats and stinging flies. When you find him, go right and jump the rats to reach the final red wheel at upper right. This dumps sludge on Ratman and the flies. Now they will chase and sting you. Go far right, then run back left and quickly climb the BIG pipe in the middle, from which you can jump to Ratman. The flies are always right behind you.