Note: Minify the command to avoid issues :)
Summon The EnderDragon
Lucky Potion with Infininite time limit
Summon The Wither Without Building It
OP Chestplate (you can fly a.k.a glide with this thing)
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)