This is a really impressive work!
It looks completely realistic and believable. The proportions and light source
are all in the right place. It is also a very detailed work, especially seen on the mouth and the teeth. The different textures look natural and are outlined through white highlights, which gives a nice effect.
I also like that it really looks like a snap-shot, though still like a fully thought-through drawing/ painting. It gives the impression of dynamic and movement.
Another positive aspect is that the viewer seems to be the object of the lion's attention, it gives a certain kind of impact.
There is actually nothing I would really critizise... maybe (just to go into detail) that the fur looks a bit too "hard" in some places and not like something really flexible. But that really does not matter.
All in all, this is a wonderful artwork and I hope for more like that!
P.S. And I would like to apologize for all possible language mistakes, I am still learning