I'm going to kill a spider.
What would drive you to kill a spider?
I will do everything to kill insects because they creep me out.
You may have an aversion to spiders, but killing them is not correct. Killing insects out of anger only creates bad karma for you.
I don't really care about karma. Plus, I grow my own vegetables and killing insects around them is ok because they destroy my garden.
Spiders will actually help with your garden pest problem as they eat insects. Your malicious killing of spiders is not correct as it serves no purpose except to alleviate your fear. Deal with your fears internally not by killing other living beings.