If you are really done with spending anymore time on it and nobody wants it (how can that be?), you can give it to charity, as you mentioned.
What you may not know is that you can donate a quilt without finishing it !
When I was able to, I used to go for a day of quilting at a local quilt shop's monthly project for making quilts for the local shelters group called COTS. We would have stacks of already made, donated, quilt tops and we put the 3 layers together with a simple quilting pattern of our choosing. The first time I did it, I got all weepy. So call around to either quilt shops or the shelters and find a place who uses tops for this purpose. This will put a positive "spin" on the quilt for you. It's very rewarding. And believe me, whoever gets it will be more than thrilled. The shelters let the homeless people choose and keep their quilts. If their circumstances go bad again and they must return, often, the quilt is their only possession. Your feeling of this frustrating quilt will be changed to a humbling and warm,fuzzy,good one.