Lion.

Lion because it's likely stronger, has bigger claws, will still have a bigger jaw

@marvelanddcfan24:

What if the dog was trained to fight,and has few years fighting exprience.

The lion was born in zoo and well feeded.

Can this change anything diffrence?

Well, yes/ It would. The lion would still be stronger, but knowing how to fight is important. For example, that is the reason lions actually kill tigers in the wild, even though Tigers are much stronger. Lions simply have to fight more often.

Lions are wild animals, wild animals have to fight like their lives depend on it very often, because they literally do. This gives the lion the edge.

In the case of an experienced fighting dog vs a lion raised in captivity, we have a closer contest. The lion will still have inherited “wild” genes but will not be a practiced fighter or killer. This could go either way I think.

Lion. Mane provides a real advantage when it comes to protecting the neck.

The lion wins.

The Dog trips the Lion over and the lion hits its head on a sharp rock. Then the dog grabs the lion by the paws and starts hitting the lion in the face with his own paws, saying "quit scratching yourself. Quit scratching yourself". Then the dog swings the lions tail through the lions legs and gives him a huge "jungle wedgie".

Holding his aching furry ball bag in his paws and rolling around in pain, the lion cries out "I give up, I give up"

The Mastiff might win if the Lion didn't have a mane.

Lion, it's much heavier and still a cat. A mastiff is (depending on breed) a guard dog, its been bred to protect not hunt and kill.

@outside_85:

It has same size was mean the dog has same height and weight as the lion.

No. Those animals have to literally fight instinctively for their lives in order to hunt for their next meal. As an example, there was a YouTube video not too long ago showing something like a mountain lion just plucking a pit bull away like the most convenient prey of opportunity with no effort at all. The lion would probably just perceive it as a baby buffalo that's easiest to catch for its next meal much more so than a real treat.