A squirrel.
And this tiny whisp of a cat did it with de-clawed front paws.
I used to know a cat that regularly caught rabbits bigger than she was. I wouldn’t be at all surprised to see one take a possum, but I have doubts about a raccoon.
Mice? check
Rats? check
Mockingbirds? check
Gophers? check
Possums? check
Weasels? check
The only thing my Londo hasn’t killed is a Narn! 
My old cat (who was fairly large, maybe 12 pounds) once dragged a big ol’ dirty seagull into the house. Didn’t quite manage to kill it, but my parents had some fun trying to chase it outside.
My mom’s cat tried to kill my dad once. That was a sharp learning curve. “165-lb guy from Pittsburgh” is definitely out as a prey item.
Very funny!
One of our cats, Devo the Tabby, weighs about 25 pounds. Though he could stand to lose a considerable amount of weight, he’s also just plain big. Based on a NatGeo show we saw recently, it appears that he may be only first or second generation domestic after generations of feral living. His teeth and claws are much larger than I’ve seen on any other cat. I have no doubt he could take down most critters his size or smaller.
Strangely, he allows me to pull his upper lip back to look at his teeth; I’ve also never known a cat that would let me do that. We think he has designated himself “my cat”, in the same way that another one, Rocco, The World’s Sweetest Ragdoll Cat, has attached himself to my wife.
My cats are constantly trying to take me down with the “run between the legs” method. When I am a little older than I am now I fully exxpect to actually fall and break a hip and then be consumed by my pets when I miss feeding them one meal.
Other than that the biggest prey they’ve actually taken down was a mouse.
I did see a 40ish pound dog at work that had the shit beat out of it by a cat. I did not see the cat but I heard it was just an average sized cat. There wasn’t a square inch of this dog that wasn’t bitten or scratched. The poor thing was in pain but he looked like he wanted to die of embarrassment.
I used to have a cat that would hunt and catch rabbits. I remember seeing her once walking across the back yard, holding a dead rabbit as large as herself by the neck; it reminded me very much of those nature films you see with a lion dragging a recently killed antelope across the Serengeti.
Our Bengal is strictly an indoor cat, but his hunting instincts are strong. Unfortunately, his usual prey is limited to insects. However, when he wants to stir things up, he’ll go after our little dog (roughly the same weight) or the big dog (about 5X his weight). Little dog just chases him. Big dog is generally not amused, and she just barks and growls.
But I suspect if he got out, he’d get himself a squirrel or a bunny at least.
My mum’s cat, Gyp, is getting on a bit (we got him as a tiny kitten when I was 14 - I’m nearly 30 now) and isn’t the cat he used to be, but he bears the scars of a lifetime spent trying to take down anything that moved. He regularly left seagull corpses in our garden - and the gulls you get on the North East coast of England are big, vicious buggers known for attacking children for their chips.
For a while we lived on the banks of the Tyne, and he moved onto rats. Mostly they were average sized, but one morning I got up, looked out of the window - and was confronted by the body of a dead rat which was more than a foot long. We had to get Environmental Health to come and take it away.
Now he’s an old man, who has hardly any teeth and dribbles a lot. He gets beaten up by the cat next door, who’s like a younger version of him. The dog has to protect him. It makes me sad. 
My friend Garth’s kitty
Believe it or not, he will not even attack a live mouse (although he will eat already dead ones).
My dearly departed Conan the Catarian took out a full grown bull racoon of about 35 pounds/15 kilo. Of course he was a monster cat himself, 21 pounds of solid muscle. He is the one that used to go out an annoy the neighborhood dogs for fun when we still lived in a town. No idea what he was, other than a basic american gellicle [black and white splotchy] shorthair.
His favorite snacks were actually rabbit and squirrel however.
There was a man who wrote a book about rats a few years ago. I heard him on NPR and he said that it was a myth that a cat could take a rat. He said that put a cat and a rat alone together and the rat would win every time. (I’m paraphrasing, 'cause it has been a long time.)
All I could think is: he never lived on a farm. Growing up I saw farm cats with rats (not mice, rats) in their mouths all the freaking time. Cats are efficient hunters.
Our cats ignore the foxes and the foxes ignore the cats.
Bobcats and coyotes win so we keep the little ones up at night.
Kittens are mostly lost to hawks, eagles and owls around here.
Ours are never allowed to get hungry nuff to go after big stuff other than a territorial challenge in their yard.
My last cat (no.4) took out a rat’s nest when he was just a kitten - they were all about his size, we think, hard to be sure as we never found a whole one.
Our first cat beat the crap out of a large dog, I’ve told the story before - very cartoonish.
Third cat limited herself to worms, and already dead things. She preferred exploring the drains beneath the neighbourhood. Odd animal.
Second cat only came into her own when my parents moved her out to the country. She was elderly, arthritic and toothless. My folks sat on their veranda and watched her bring down a full grown male duck.
The long-departed Tulip took on a mink at our summer cottage. The screaming, cursing and general bad language was incredible - all this in the dead of night - when the back door was flung open and the flashlight was shone upon the combatants the mink took off at speed, dusting him/herself off and flinging one more insult. The cat, OTOH, did an immediate about face, bolted into the cabin and under the woodstove and would not come out for about three days.
She was, however, a mighty hunter of deer mice.