The World of Chaos. You can see Ansem is stuck on it.
The World of Chaos is the final boss in Mario: Defender of the 20 crumpits. He appears when Ansem fuses himself with The Darkness and transforms into a huge monster. With Chuck inside it, The boss has not been defeated yet. The longest anybody lasted a battle with it was taking it's life down to 70/100 life. He also appears in
Mario Tag as the final boss of the game of Adventure Mode, and appears in the Boss Run mode as well.
The battle with The Harvester[]
In Mario: Defender of the 20 crumpits 2, it appears that Chaos has survied, and in the last cut scene before his final battle again, he battles The Harvester. In this battle, Chaos uses force power to crush The Harvester into a metal ball. Then, you battle him again. Many of the fans say they made him harder.