Notch Boss Battle (Almost impossible to kill ALMOST)
Note: Minify the command to avoid issues :)
Archer Boss
Hostile Archer (1.9.1)
Weakest sword in history of Minecraft no mods !!!
More mobs in 1 command (Read The comments!)
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)