Easy "Apocalypse Ciao Badge". Make sure you have a max upgraded boomerang dojo. Start with 1 boomerang monkey against 1 of the corners where the lava flows out and upgrade to 2/0. Buy another as you have enough money, place in a corner at the other side of the volcano. Upgrade it to 2/0. Next upgrade 1 of them to 2/2. as money comes in continue to buy boomerang monkeys upgrade to 2/0 only. and always place in a corner until all 8 are filled. Easy level 30+ on apocalypse mode for the badge :)
 "Bloons TD 5"){kind=icon}
 "Lucky Tower 2"){kind=icon}
 "Decision 2"){kind=icon}
 "Jimmy Bubblegum"){kind=icon}
 "The Story of Jimmy Boy"){kind=icon}
 "Arkandian Revenant"){kind=icon}
 "Epic War 3"){kind=icon}