And Good Riddance!

Total purification: not one block of Corruption, Crimson or Hallow left, until the Dryad's status check reads a clean 0% of each. The Clentaminator with Green Solution (from the Steampunker) is the tool; the method is systematic coverage - a grid of hellevator shafts across the map, sweeping spray runs along each, and the Dryad consulted between passes. Underground pockets and single stray blocks are the tail; explore the map fully so remnant colour shows on it. One of the game's longest tidy-ups - budget a few sessions and podcasts.