they just added bats.
witherboss
Wither Boss
No version of the vanilla minecraft lets you tame a 'hostile' mob, that's something added by a mod. (Wolves are a neutral mob until attacked, they can only be tamed while neutral, not while hostile)
The mob with the most HP in Minecraft would be the enderdragon. The Iron Golem which is a mob you can summon or craft also has 100 HP and is very powerful killing zombies, skeletons, spiders, and slimes.
Go to minecraft wiki and do a search for "mob grinder" and it gives you a tutorial of how to do it.
Chickens are passive mobs that first appeared in Alpha mode.
You cant find a giant mob in vannilla minecraft but you can sumon him using a command or a spawner.
no
a bat
Mobot
by using spawn eggs or mob spawners with a mob in them
a monster mob in minecraft