The Calabar Burrowing python. It is a very small fossorial snake that can not move fast enough to escape predation or catch prey, and has a very weak bite and constriction ability. It preys on baby mice which it either simply scoops into it’s mouth or squashes them against the side of the burrow to kill them. It literally sits on them to kill them because it is so wimpy. It has no defense mechanism other than to hide it’s head, tuck into a ball and offer a proper predator it’s fatty tail section which looks just like it’s head.
ETA: I started writing this a couple hours ago when Waxwinged frog’s post was the last.
OP here.
Thanks all, I was hoping this didn’t sink like a stone. And yes, I recognize that the OP is vague.
I agree with the folks who suggested filter feeders like whales vs. krill should be excluded on the same grounds as terrestrial insectivores. I’d thought of that condition but left it out of the OP in the interest of brevity.
And I agree in a scientific sense with Blakes complaint about lousy predators being omnivores which if considered, then shades our candidates smoothly all the way into sheep which occasionally chomp a mouse. But that’s a distraction from my actual purpose.
And yes, I didn’t specify whether I wanted relative or absolute ferocity/wimpiness. e.g. A lion can kill bigger prey than a wolverine can, but on a pound-for-pound basis my money’s on the wolverine. I left that point out because I wasn’t sure whether Mother Nature had a better candidate on the absolute or the relative scale.
The rest of the story …
My original interest was to create a rhetorical device, not necessarily obtain zoological precision. When you want to say something or someone is especially fierce, you make a simile to a lion, a grizzly, or perhaps a wolverine. (Thus exposing the relative/absolute conundrum).
So I wanted a sarcastic, joking or insulting anti-compliment: “He’s as fierce as a ______”, where two ideas come through clearly: 1) The animal in question is one people recognize as a predator, a killer. 2) The animal is inept, cowardly, ineffective, etc. at it. An alternative formulation is “He’s ______ prey.”, meaning this guy is so non-fierce that even our putative wimpy critter could have him for lunch.
“He’s tiger lunch” or “He’s mosquito lunch” aren’t exactly stinging insults; all of us are both.
There’s an implicit point that the prey in question be human. So we could go with either big predators with low absolute ferocity or smaller predators with larger absolute ferocity. Whichever works better.
And yes, this brings up a further contradiction, between critters commonly know to Joe Public, and the actual wimpiest predator which is probably some obscure Patagonian micro-rodent.
Here’s an anecdote which might help …
When I was a kid we got a new puppy. One day when he was about 8" long he proudly brought us his first “kill”. It was a snail. Now *that’s *a fierce predator. We all had a good laugh at his expense. He was so proud & so earnest about it. Good thing he didn’t speak human yet.
“He’s squirrel prey” would work great … but only if folks knew that squirrels kill & eat meat. Which most folks, myself included, do/did not.
Thanks again for playing along. And yes, this is silly.
Late add. Acid Lamp’s Calabar Burrowing python nailed it.
Maybe the North American Gray Wolf. There have been very few documented attacks on humans by non-rabid north american wolves except when the human was clearly starting something.
European wolves is another story. And it’s not like a pack of wolves wouldn’t be able to take down a human – one would probably not be able to take down even a weak fully grown human without risking life-threatening injury, but a whole pack of them should be more than a match for any human. But they don’t.
As opposed to mountain lions, who do attack humans regularly by themselves and they are barely a match for us physically (smaller in size but stronger and stabbier.) Those are some brave mofos, compared to the wolves.
If that’s the intent, then I might go with something like “He’s possum bait.” I think most people would recognize that opossums take some animal food, but are not very fierce. And if attacked, they’re more likely to play dead than resist. If you want something more exotic and fun to say, try kinkajou.
Alternatively you could go with something that’s big and ostensibly powerful but generally inoffensive, like a panda. (Although in real life pandas are capable of doing some damage.)
If you want a really small predator, try a weasel or maybe a shrew. Although ounce for ounce they are probably the fiercest predators around, they aren’t going to do much damage to a human.
I would go with the Giant Panda. From the standpoint of taxonomy, it’s a carnivore, and still has carnivore traits, such as its digestive system. And as Colibri observes, it’s capable doing some damage - it’s a BEAR fer God’s sake. However, it eats mostly bamboo … inefficiently. What we have here is a “predator” that was so wimpy it gave up on the idea.
Plus it was a mother defending her cubs. If she’d been on her own she might well have run off but animals will do downright stupid things if they’re worried about protecting offspring.
I think that the wolves deciding not to attack humans doesn’t make them wimpy. Like other pack canines they gang up to take down large animals but for the most part choose (and that’s the operative word) not to have people on the menu.
A marine researcher once pointed out that if sharks decided they wanted to eat us we’d have no more survival chance than krill and the fact that shark attacks *on people *are statistically rare does not mean that the sharks are wimps.
Frankly I would like to thank the wolves for not giving me an additional item I can stress about on my hikes in the woods.
Can we swap in “kitten” instead of “cat”?
Still, in terms of the OP’s clarification, a wolf would hardly qualify. Most people are going to think of a wolf as fierce, even if they don’t regularly attack people.
I have little doubt that a single full-sized wolf would be quite capable of taking down the average human if sufficiently motivated. A large or very strong human or one with training could fend one off, but I think most people aren’t going to be quick or strong enough to prevent a wolf from getting at their throat, and after that it’s over. They would have a better chance against one of the smaller breeds of wolves.
A fox maybe?
What about something like the Ringneck snake. It only grows to about a foot in length and feeds on earthworms and small salamanders. It is a carnivorous predator that feeds on animals much smaller than it’s own size, and doesn’t bite humans. Feel the fear . . . .
If we’re going there, then I nominate the Earth Snake. We get plenty of 'em around here - in fact, I just rescued one off the sidewalk yesterday. It was cold and torpid. I picked it up, continued on my walk with it curled in my cupped hands until it warmed a bit and I’d walked to a spot with suitable habitat: rocks, plants, etc.
It was easily the biggest one I’d ever seen, at a whopping 4 inches of so in length. 
They eat pillbugs and small worms, and can’t really bite a human even if they were so inclined - that tiny mouth just can’t fit.
Blind snakes are even wimpier.
They don’t even eat termites whole - they suck out the body contents and spit out the skin.
The smallest species, and the smallest snake in the world, is the Barbados Threadsnake.
Well that and the fact that thing can totally kill you by ripping open your guts with its giant claws that it uses to dig into ant mounds. (Which are supposedly as hard as concrete. The ant mounts I mean.)
SHORT answer?
Humans.
Whilst overall omnivores, humans DO prefer to eat meat. See Texan for a prime example. 
Seriously though, humans can’t outrun much over a turtle. Humans have some issues even fighting a snapping turtle, which CAN disable a human by biting off a finger.
Humans have only TWO traits that contribute for their rise:
1: Tribal nature (aka pack hunters).
2: Forethought and planning.
BOTH contribute to make humans capable of rising to dominance, as a GROUP. See bear kills kid or dog pack kills person stories in the news…
Between the Calabar burrowing python, the kinkajou, the opposum, and blind snakes I think we have some great wimpy critters.
I think the kinkajou wins overall because in addition to everything else, it’s cute. Like the very fierce bunny in Monty Python and the Holy Grail, the cuteness adds a nice twist.
Thanks all.
[QUOTE=Wizard One]
SHORT answer?
Humans.
Whilst overall omnivores, humans DO prefer to eat meat. See Texan for a prime example.
Seriously though, humans can’t outrun much over a turtle. Humans have some issues even fighting a snapping turtle, which CAN disable a human by biting off a finger.
Humans have only TWO traits that contribute for their rise:
1: Tribal nature (aka pack hunters).
2: Forethought and planning.
BOTH contribute to make humans capable of rising to dominance, as a GROUP. See bear kills kid or dog pack kills person stories in the news…
[/QUOTE]
Humans don’t run fast as large predators goes, but they have far more endurance than most furry animals. They can run down an antelope until it stops due to heat exhaustion. This is called persistence hunting. It is a method still in use among the Kalihari bushmen.
Humans are bigger and stronger than the majority of mammals, fish, and birds. We’re not well armed with teeth or claws, and we don’t run very quickly, but we became very good hunters. We on the SDMB are mostly civilized, and lost the skills that made us good hunters, but that’s a matter of skills, not capability. We don’t take on snapping turtles because we’re afraid of losing a finger, not because we can’t. When it’s ‘catch the snapping turtle or die of starvation,’ we are willing to take the risks. There’s a reason why extinctions of large mammals took place on every continent we moved to, and it’s not because we played our music too loud and drove out the local fauna.
Yeah, we’re social animals that hunt in groups. So are wolves and hyenas, and the latter kill lions. Come to think of it, so do we.
I think humans is the closest thing to what you’re looking for. We’re pretty weak even compared to most herbivores (could you chase and tackle an antelope in full flight?) and we have no real natural weapons or defences to speak of - no claws, puny teeth, weak skulls, exposed bellies. For the first 5 years of our lives, at least, we’re completely helpless. Even when we hunt successfully it tends to involve being sneaky rather than being forceful: we catch fish by dipping into the water and surprising them; we tend to hunt land mammals by hiding and then throw weapons at them from a distance with an element of surprise, or setting traps for them; endurance hunting involves deliberately chasing an animal until it collapses from exhaustion because we’re not strong or fast enough to catch and kill it like cheetahs do. In the wild we’d spent most of the time hunting animals smaller than us, or foraging for herbivorous food instead.
Very little human hunting behavior ever involved catching and killing prey in the same “fierce” way that tigers or sharks do, and I’d back the average human to lose any stand-up fight with any other animal mentioned in this thread. Try cornering a fox and see if you can kill it. Hell try cornering a wild cat or dog and see if you can kill it. Humans are a seriously wimpy species physically; we’ve just gambled that brainpower would be more successful in the wild, and we were right.