So. Go to end. Make command block to do /execute NAMEHERE ~ ~ ~ summon tnt 1 (Btw why tnt 1 explodes instantly? It used to be like alpha tnt) and then go on /Gamemode 3.
Fly to the enderdragon and spectate him. Yes. You cant jump and spectate dragon. Thats bug number one.
Then, see if there is explosion on dragon.
Game thinks you are spectating dragon IF you are standing still and tnt explodes at dragon. If you move, 1 tnt explodes at you, second one at dragon, another at you and at dragon etc. I will try to upload video. Probably low quality, but still. I wanted to count how many tnt it takes to kill dragon.
I will post video later if possible.