Complete list is here: http://www.cracked.com/article_15816_5-most-horrifying-bugs-in-world.html
The Killer Jap Hornets!!
30 Hornets pwning 30,000 Bees; chopping their heads off of their bodies
https://www.youtube.com/watch?v=6fTrSOFyfxs&eurl=http://www.cracked.com/article_15816_5-most-horrifying-bugs-in-world.html
Bullet Ants!
they sting like getting shot from a bullet!
https://www.youtube.com/watch?v=9WQ6rFKhyn0