VERY WEAK!
Note: Minify the command to avoid issues :)
Player Heads minecraft redstone
Better EnderDragon (4 commands)
Mobs with special abilites! only ONE command! 1.8.7 (Read The comments! )
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Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)