By fighter I mean what the animal can do besides bite also this is a measurement based on skill, not raw strength. Make sure to explain your reason why.
The mongoose has the ability to fight and kill venomous snakes, particularly cobras. They are adept at such tasks due to their agility, thick coats, and special receptors that render them resistant or immune to snake venom. I have heard myself that the reason they are immune to venom and can fight snakes so well despite their puny appearance is because when the first time a mongoose and snake fought, the snake killed it. The second time, the same result. But the next time, the mongoose was able to fight back. Over time, they evolved to be able to kill and eat snakes almost effortlessly.
Offensively: Roadrunners. They're fast enough to bulrush you and land several hits before you can land just one, skilled enough to dodge anything you throw at them, small enough that they're hard to actually hit in the first place, and they know exactly where to peck at you to bring you down. All of this is best shown when they fight Rattledsnakes who can literally kill them in one hit if they're not careful. The reason I don't have them as the best fighters is because there is another animal who uses its advantages better.
Defensively: North American Porcupines. What separates them from other Porcupines is there quills have barbs which make it harder to pull out and they can use those quills to great effects. You literally can't touch them without getting stabbed. If that doesn't count then the rodent like creature that lives in the desert because they can outmaneuver Rattlesnakes and trick them into striking by filling there tails with blood. Anyone know the name of what I'm talking about? Either that or Cats because they also take hits like a champ which I'll explain in a few.
Smartest tactically/best in groups: Gray Wolves. They can actually use tactics to take down bigger animals like Moose by swarming them from different angles.
Overall best: Cats (you heard that right). Just like Roadrunners they're fast enough to bulrush you (I'd argue they're the fastest for there size), they're skilled enough to dodge attacks, etc. Unlike Roadrunners, Cats are durable enough to take attacks that hit them, they can instantly recover from hits and falls by landing feet first something most other animals can't do, and they're pretty versatile even though they often only use a hack&slash mixed in with a wrestling technique. They are also pretty smart often letting there enemies make the first move and countering from there.
The scorpion is pretty good.
It's claws are very powerful given its size making it very tough for even badger sized animals to tackle easily. If that wasn't enough it has a stinger which can incapacitate small mammals and kill most invertebrates
I don't know if there is a kind of scorpion with both powerful venom and powerful claws. All of them seem to have only one of each (deathstalker scorpion: only powerful venom; emperor scorpion: only powerful claws etc.)
Defensively: North American Porcupines. What separates them from other Porcupines is there quills have barbs which make it harder to pull out and they can use those quills to great effects. You literally can't touch them without getting stabbed. If that doesn't count then the rodent like creature that lives in the desert because they can outmaneuver Rattlesnakes and trick them into striking by filling there tails with blood. Anyone know the name of what I'm talking about? Either that or Cats because they also take hits like a champ which I'll explain in a few.
Smartest tactically/best in groups: Gray Wolves. They can actually use tactics to take down bigger animals like Moose by swarming them from different angles.
Overall best: Cats (you heard that right). Just like Roadrunners they're fast enough to bulrush you (I'd argue they're the fastest for there size), they're skilled enough to dodge attacks, etc. Unlike Roadrunners, Cats are durable enough to take attacks that hit them, they can instantly recover from hits and falls by landing feet first something most other animals can't do, and they're pretty versatile even though they often only use a hack&slash mixed in with a wrestling technique. They are also pretty smart often letting there enemies make the first move and countering from there.
Any questions?
It's claws are very powerful given its size making it very tough for even badger sized animals to tackle easily. If that wasn't enough it has a stinger which can incapacitate small mammals and kill most invertebrates