My fierce dog.

A Labrador Retriever should not be aggressive in any way. The FCI Labrador Retriever standard says that "Aggressiveness towards humans or other animals in an adult should be severely penalized." If your dog was bred by a responsible owner, you shouldn't have this behavior. But Labrador is a very popular breed and many irresponsible people bred dogs without considering the bad temperament of the genitors. This is how aggressive Labradors can be frequently seen nowadays. That's too bad that the correct image of the breed is spoiled. I suggest you to neuter your dog to decrease his aggressiveness toward other dogs. You should also start an obedience training program to make him respond to your commands. He is supposed to stop barking/jumping on the gate when you ask him to.

My dog is like that as well. Whenever she sees another dog, she became so aggressive. But my dog is very sweet to us however too fierce with other dogs.

Your dog will remain aggressive towards other male dogs as long as he is not fixed. Dogs who have not been fixed tend to have more dominant and territorial personalities. You should consider getting him neutered, our dog is fixed and he is one of the sweetest, goof ball ever, and he loves other dogs.

Labs are naturally jumping dogs and might not necessarily connote fierceness, I think it's a natural reaction when there's another dog but the labs size and power plus the loudness of it's bark would make us interpret it us fierceness, Labs are one of the gentlest breed of dogs and are quite safe even with children ( dog experts say this), that's why it's always on top of most popular dogs in the U.S.I once had a lab that would pounce and jump and bark on people and even frighten friends but the only think it wanted to do was leak my face when we see each other, not advisable though if you have small children cause might knock them down. To make him stop, you have to tire him by making him run in a large yard,play fetch ( he has natural retrieving instincts), everything a lab loves and give him cold or ice water to drink and plenty of water to play in like a large basin(labs descended from an extinct water dog) Good luck