Defeating him has nothing to do with milk.
There is no milk to be found anywhere on Super Power island.
Turn the red wheel on top of the last ledge.
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.
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.
Ratman is hiding in the sewer under City Park, with his pet rats and stinging flies.
Ratman is on Super Power Island. There is a large rat in the sewer entrance to the factory on 24 Carrot Island (climb up into the bypass pipe to elude him).
The pay phone will ring when you have defeated the first 5 super villains (Copycat, Speeding Spike, Sir Rebral, Ratman, and Crusher). Answer the phone and you get the power to fly! Then you can defeat Betty Jetty.
You can beat the 5 non-flying villains in any order. If you are working left to right, the next is Ratman in the sewer under the restrooms.
The pay phone will ring when you have defeated the first 5 super villains (Copycat, Speeding Spike, Sir Rebral, Ratman, and Crusher). Answer the phone and you get the power to fly! Then you can defeat Betty Jetty at the skyscraper (Downtown).
You can defeat the 5 villains in any order. Copycat and Speeding Spike are Downtown, so the next villains are Sir Rebral in City Park and Ratman in the sewer under the restrooms.
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 6 escaped villains to recapture. The first 5 are Copycat, Speeding Spike, Sir Rebral, Ratman, and Crusher. Once you have captured them, you receive your super flying power to chase the 6th, Betty Jetty.
u spin the weel and a bunch of gunk comes out