Hard b'stid

a swan will break your arm if it's driving a transit van.

but a honey badger can swallow chewing gum and live

hmmm…i'm still alive 😕

Hyena, bone crushing nutter.

Preying Mantis- no contest, the little green bastards seem to think they are 6 foot tall or something try approaching one and delight as it sets about trying to kill you with its weird back to front elbowed serrated arms.
Nutters.

my vote goes to the polar bear. always wanted one as a pet when i was younger. only problem is the house isnt quite big enough. maybe when i move.

There's something to be said for the Komodo dragon. Pretty tough to start with, runs fast as hell, bites you then follows you around until you die from the infected bite. Oh and Billy Bob Thornton thinks they're evil (but he also has a phobia of antique furniture)

Chimpansys r wikid smart so they can use wepons chimp with nukeldusters and baseball bat can beet orangatang or babbun

Can you try that again in English?

Elephants are pretty hard too. Except they dont go around broadcasting it. Every animal just knows you dont mess with an elephant. (A fully grown one anyway)

kills millions every year

+1 for that Honey Badger, just watched that you tube clip, proper beast ! wait till all the chavvies see that, theyll be ditching their staffies and start walking (or be dragged around by one of them) in their tracksuits. (the chav in the tracksuit not the honey badger) mind you the chavvies round are way are that thick no doubt the odd one will be seen trying to walk a box jellyfish on a lead

Mate used to hunt boar in Oz with a large knife and 2 dogs. Could be hairy at times. Dogs wore armour. I'd run along as a beater carrying a stout pole for fending off the boar.

Personally I preferred a cut down Rossi with Brenneke slugs for the job, but you had to get real close to use it because it wasn't very accurate.

Quite often the boar hunted us. Could get a bit exciting. Recommended as interval training.

2nd Mantids.
I have seen one stood by the side of a busy road trying to take on all the cars as they sped by. I tried moving it safely away and it went psycho on my ass.

This is a horned baboon tarantula asking for a kiss kiss. She can be a bit uppity.

Personally though, the hardest or scariest are parasites which take over their hosts functions and mind. Eat and control from the inside, the host knows but can't stop it.