I tend to like all breeds but there are a few breeds that I would never own, I know I wouldn't be able to handle them.
Chow chow is the only breed that I can think of that I don't really like. I've met a ton of chow chows and chow mixes and every one of them was mean. I know it's mostly not their fault though, I know the breed well and I know they take a more firm and very experienced owner to turn out right.
My dad has a chow/golden retriever mix. She is sweet with me as I've known her since she was a puppy. But to any stranger she will immediately bite them. When they take her to the vet they have to sedate her and muzzle her because she is that aggressive.
I have no idea how she turned out this way. They socialized her, did everything they were suppose to.