AHAHAHA!
I'VE DONE IT!
I just beat the dragon with NO ITEMS! This excludes anything you can obtain without mining on the main end island (enderpearls, mainly), and chorus fruit (so I don't starve to death, because I was on hard mode).
This took me multiple attempts and on the final attempt I beat it in 3 hours 20 minutes. I died 19 times. I challenge everyone to beat my number of deaths. I will be posting on Reddit the exact rules very soon, along with the video I recorded of the challenge.
Good luck dying less than 19 times... and remember, record the whole thing or there's no proof!
When done uploading, the unedited version of the video will be found here