I will be the oddball here and assume that the chick was dead upon cracking...my main presumption is because there isn't much blood in the shell or leaked around the baby...as I have found, if I mistakenly crack an egg that the chick is alive in, the membrane immediately bleeds profusely...that didn't seem to happen here so the chick was already dead.
OP, just looking, I would say the chick was at approx day 16-17 when he/she expired. Also, it seems very wet...what was your humidity at? I recently attempted a "dry hatch" wherein I added NO water to the incubator AT ALL until day 18. Then I added it to all reservoirs and even wet a washcloth and left it inside. I had a 100% hatch of 3 eggs!
Don't beat yourself up...my first few hatch attempts failed abysmally...and I have found that slight variations in temp don't seem to harm my hatches...my bator usually runs between 98-102 but if you mess up humidity too much, you're in for heartbreak. Just this hatch I was actually shocked it turned out so well. On day 15 someone unplugged my incubator and it got to 70 degrees before my dear husband found it and re-plugged it in! They can survive much but if you have high humidity throughout the process, you will have heartbreak everytime.