No, she's not the worst character. She's the worst villain. You would think that the one who accesses chakra and is the manipulator of all chakra in the universe would be intimidating and badass, but this woman is neither one. There are too many flaws in her character and there are still many things that are unexplained.
If you need someone else to coordinate your directions and tell you what to do, mind you this is a fcking Zetsu, then you are indeed a terrible villain.
When Madara was the villain, there was actually a sense of danger and cry with him. You actually wondered how the SA would survive. When Madara sent down that meteor, that was the epitome of chaos. When Madara soloed the five Kage with relative ease, that was the epitome of chaos. When Madara the Juubi Jinchuriki and stole Kakashi's eye, that was the epitome of chaos. When Madara summoned those CT on the field, that was the epitome of chaos. When Madara soloed the 9 Bijuu all at once while being blind and caused the near deaths of Naruto and Sasuke, that again, was the epitome of chaos. When Madara finally started the IT, that yet again was the epitome of chaos.
Now we have Kaguya over here, who got punked by Rikudo Sage Naruto many times and ended up being sealed in less than 15 chapters. Are you serious? What did she display? A bone technique that pales in comparison to Kimimaro? Basically the only thing that she was doing this entire arc was change dimensions and run away like a coward. Her only game plan is dodging attacks, blocking attacks and running away. Really? Is that all you can do? Kaguya didn't do shit that made a major impact on anyone.