Ticks. Ticks are the only animal I would honestly consider driving to extinction if I had the opportunity.
I think I have a phobia of them at this point, since they harassed me so much in my childhood. I liked playing in the forest, so all the little fuckers would come out and bite me. Of course you typically don't notice that since they are so small and slow. A few days later I would run my hand through my hair, and then feel a small bump. I'd touch the bump a few more times, hoping it wasn't what I thought I was. Of course it always was. Then my mom would get the tweezers and alcohol, and we'd spend 5+ minutes in the bathroom trying to dig the tick out of my scalp. Most of the time my mom would remove the body, only to find that the things fangs were still embedded in my skull. Another 5+ minutes in the bathroom.
Now that I'm older, I haven't been bitten by a tick in a long time since I'm much more paranoid about them. But the little bastards still find ways to annoy me. On a recent hike, I emerged from the brush then collapsed onto the grass, looking up at the beautiful blue sky as bird chirped off in the distance. Then I noticed about 5 ticks crawling on my pants and shoes. I went hysterical, and spent about 3 minutes making sure there wasn't a single tick anywhere on my body. This was actually entirely justified, since I found one embedded in my shoelaces right before I left. Aside from trying to bite me, ticks also bite my dog frequently.
Without any redeeming factors to name, ticks have earned nothing but bitter contempt from me. To top it all off, seeing a tick fully bloated with blood is a truly grotesque sight. So yeah, ticks such.