What's the most difficult plant for you to grow that's supposed to be easy?

For me, it's zucchini/yellow squash. I can grow nice, large zucchini plants but spend the entire season babying them for little reward. Between needing to hand pollinate and fighting off pests and powdery mildew, I'm not sure if it's worth all the effort in my case.

If I do try again I'll look into parthenocarpic varieties. Varieties with resistance to powdery mildew don't help much in my area, which is coastal.