you can choose any mob you like!!!!
Note: Minify the command to avoid issues :)
OP Chest version:1
WACKY STICK
HEALTH BOOST 10 (not absorbation!!)
OP version:2
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)