Mixed dog breeds, aggressive Lab/Rot.

I think the person who sold a Lab/Rot mix to an 80 years old lady is a irresponsible person. He (she) should have known from the begining this dog is not good for an old lady. He must be such a bunch of energy she could hardly manage! Sometimes it's hard to own a huge dog for a younger person, but for your aunt must be almost impossible. It is never too late to train a dog. Your aunt's dog is still young and you'll have good results with his training. Whether you train him or you take him to a professional dog trainer, in both cases your aunt should be the one to be able to mastery the dog. So go for it! Train the dog and see the results.

I do not think he is too old to be trained, but with such a demanding dog, you might want to consider asking a pro to do it, instead of trying to do it yourself. It does not have to cost a lot of money to ask a professional dog trainer to do it, and even if it does, you only pay this amount for a very short while, so it should still be worth it, if the results are really good.

Kill it! JK Anyway, as people say late is better than never so just train him again.

Well dogs are dogs. When they grow up, they can be aggressive. I also did own a mixed breed Labrador once. He was somehow tame. As for my friend who owned a doberman, it also bit her daughter and she wanted to give it to me as a present. I turned it down.