irontastic!
Note: Minify the command to avoid issues :)
A nice firework
Firefighter's Items in one command
BlazedWither boss (Literally unkillable) Read the comments
Evil Golems in 1 command
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)