This guide will tell you how to get these confusing achievements…
The Hell
For “the Hell”, select “New World”. Then create a tiny world.
Fill the entire world with forest soil, than cover every tile with infernal seeds.
Next, you spawn about 100 demons. If this does not work, than just keep spawning demons till you get the achievement.
Let’s Not
Next, for “Let’s Not”, turn the entire tiny world back to forest soil. Than, use the acid rain tool to cover it in the wasteland biome. (Poor Acid all over the soil) Next, you use the atomic bomb on the wasteland biome, and you should get the achievement.
By HiszorN