When fighting the dragon in the end, my game crashed. When I loaded back in the dragon had her full health and she wouldn't take damage. As most would think, this is quite a big issue. Also if it helps, I was in peaceful, (because im a coward.)

Also I made a backup of the world so I can test the bug, basically, what I presume is the game thought since my game crashed that there wasn't a dragon, so it spawned another. However somehow deleting the other and some weird stuff happened that leaded to the dragon not taking damage. So by just using commands fixed it, I find that to be challenging in my main world where cheats are off. (i also have no clue what i just said, i just know the game spawns dragons when it thinks there isn't)

mb, couldn't find if this was a duplicate.