For all chapters - Upgrade your Cat Wallet to max level, when enemies are near to your base, send out few Tank Cats/Wall Cats. They will act as a stallers. By the time Kang Roo appears, your money should be maxed out. That's when you can send out all of your basic cats. When you will kill Kang Roo, all other enemies should be a piece of cake. Finish them down with Gross Cats/Sexy Legs Cats and Bird Cats/Ufo Cats. Another Kang Roo will appear when you hit the enemies base, but he won't be such a big threat anymore.