Heather, your difficult child sounds depressed to me. As you probably know, anxiety and depression can go hand-in-hand and spill over into each other. I recognize this negativity and holding grudges forever in my own daughter, but when we got her properly medicated, these symptoms subsided to a large degree. Perhaps your difficult child's medication is only partially doing its job.
I'm reading a really interesting book about a depressed suicidal teen called Will's Choice by Gail Griffith. It talks about how some depressions are only partially treated with disasterous results. You might want to check out this book.
