When asking about the authenticity of pictures, you have to provide references.
… this is a picture of actual bones edited together with a picture of actual people to make the people look really small (or the skeleton really big, depending on what you like to imagine).
On the other hand:
… this is not edited. However, the skeleton is an art installation and was never part of a living being.
As a simple matter of physics, a skeleton that size and shape is unable to support it’s own weight, and that skill would break it’s neck if it ever tried to stand upright. Any actual giants would need to have really thick legs, and tiny (in comparison) heads.
… this is a reconstruction from fossils of a real skeleton of a real living creature that was really big. See how fat the leg bones are and how small the head is by comparison.
… this is pretty much at the limit of maximum possible human size. he has to walk with a cane to avoid breaking his own bones just standing up.
So… compare the pictures you see with what you now understand about giant skeletons and see if they stack up.
Fakes can get pretty good … the best approach is to disbelieve anything you can’t verify. meantime, learn how to verify.