While personally I wouldn't want to minimize the experience of someone in Guantanamo bay, I can say that the end of my mom's life was worse than the most horrible thing I can imagine, and if I ever face a serious risk of that fate I'll be packing my bags for the border.
My mom's cancer metastasized to her bones, among other places. Bone cancer is apparently the most horrible thing that can happen to someone. The tumors cause pressure inside the bones that cause them to slowly break. The bones are too damaged to heal, so they just stay broken. The cancer also weakens the unbroken bone, and as it progresses they break more easily. She would just sit and cry because she was in so much pain. She was on about as much pain medicine as hospice could give her without killing her, and it only dulled the pain. It's not possible to give someone enough pain medicine to take the pain from bone cancer away. Hospice flat out told us that. She was eventually confined to a bed because her bones had thinned too much for her to safely move. She was pretty stubborn and spirited, and would occasionally sneak out of bed - only to fall and break her arm again. Imagine being confined to a bed and being so bored that breaking your arm is more interesting. From what I understand, it's common for these folks to kill themselves before the end comes, because it's just so goddamn painful. I wonder sometimes if my mom died as the result of being on so much pain medicine, because quite frankly, sometimes hospice tries to do people favors. I wasn't in favor of her killing herself but she really didn't want to live anymore.
That doesn't include the pain from the tumors in her abdomen, or the batshit insanity brought on by the tumors in her liver.
Oh and before that there was the psychological trauma from watching her go from being small and attractive all of her life, to a size 1x and being so swollen she was purple from pooled blood, and then watching her melt into a yellow jaundiced skeleton. Some of the last words she squeaked out were about how horrified she'd become of her appearance, which brought her to tears. So there's that.