I think the intended logic behind this thread is not to point out which discs suck, but which discs have disappointed us the most to the point of hatred.
As for the Groove, Katana, Nuke SS/OS, Wahoo, and so on, we all knew what we were getting into when it was announced that yet another wide rimmed driver is coming out. Anyone who truly believed that the latest wide rimmed driver was going to be different, going to be that one magical disc that can cure your game, then I can understand the hatred. Anything beyond that is just a refusal to believe your long game sucks more than you would like and you need something to blame like a disc. I think the Flow, Havoc, Vulcan, and to a lesser extent the Archon may soon fall into this category.
With that being said, I generally hate discs that are routinely being hyped as great discs, raise my expectations, and then fly nothing like being described. Like earlier, it is the thrower, not the disc, but I hate the X-Predator and C-PD; money not well spent. The Vector and Gold Line Pain are on the tier below hate, and I have a love/ hate relationship with my soft Ions.