Lab Puppies and lab dogs are pretty gentle and loving dogs but just like any other breed of dog the lab puppies or fully grown lab dogs can become aggressive especially if they become taunted etc.
Never let kids or anyone taunt the lab puppy or lab dog including any breeds of dogs.
That leads to any dogs including lab dogs to become aggressive and decide to attack people or children.
Treat the Lab puppy or lab dog or any other breed of dog or puppy nicely then they'll likely love you back and not turn aggressive.
However some breeds of dogs such as Pit Bulls are naturally aggressive and can turn on their owners without warning even when you treat them nicely.