Let the spiders steal candy 100 times
You can let the spiders steal candy just by not cutting the rope they are on with the candy. Eventually they will get to it and you will fail the level. The best level to grind this on is 2-15. A spider goes after the candy right from the start of the level. Just load up the level and don't do anything for 15 minutes or so and the achievement will unlock (touch occasionally to prevent screen timeout). After the spider gets the candy, the level will auto-restart.