In Conan Exile, to remove corruption, you have to kidnap some dancing girls and wait for Stockholm Syndrome to kick in and then watch them dance. I guess buying something from an NPC could work, but then how would the dancing girls earn a living?
I have Terraria, but I have a mental block about open-world side-scrolling games. Maybe I should try it again.
Terraria is not an open world, you generate a world with clear boundaries on all sides. You can take your character into a new world with all of its equipment, but there's no real need to do so unless you somehow really screw up your existing world (for example if you let everything get covered by corruption/crimson).
Sadly the thing that removes corruption is too expensive for me at the moment, but I have managed to stop the spread of the crimson above ground with some air gaps and a bunch of purification powder, which is cheap but only works on small areas.
I have also defeated all three mechanical bosses now, with the help of my new minigun (though it still took two tries for both of the remaining ones). Sadly they didn't drop enough to get both the new tier armour and the new tier pickaxe, so I'll have to summon and kill one again.
Once I do that I can move on to get the next tier of equipment and kill Plantera, which then also slows down the spread of the Crimson.