Took me a while to realize what was happening here. Very funny. For anyone who wants to know the answer to the question of how to stop corruption in terraria: You dig big holes down both sides of the biome down to hell and make it at least 3 blocks wide. This is one of the most reliable ways to capsulate it. Then get that clantaminator from the Steampunker and get that green stuff from her too. Then go to town on that biome you just separated from the rest of the world.