If あなた could rid the world of ONLY one thing, what would it be?

That's a really bad idea... Spiders are an important part of many ecosystems. Chaos would break loose in the animal and plant kingdoms of they were all eliminated. Not to mention there are so many other things that are so much worse in the world. Even in the short run, in the selfish and ignorant scope of humans, they only pose a minor nuisance to us.

Well said. I've got to admit you're right. I kinda just spit this out. I didn't even thought much about it.