I hate hemlock.
I don't try to make the woods into a park. I normally leave things pretty much alone (aside from keeping grass and weeds choking the paths knocked down). Even poison ivy I leave where it grows.
But hemlock has my undying enmity. As does ailanthus. Thank God kudzu doesn't grow this far north (yet?). Hemlock, ailanthus, and kudzu form the unholy trinity of weeds.