He doesn't look natural. Sorry...

Well, as you specifically request comment, I will supply:

I think you need to concentrate on anatomy; there are many things misaligned here. many of the elements work well on their own, but are either misaligned or of the wrong size compared to the others. It's most apparent on the mouth, which I believe should be slanted a bit more downwards at the right, and is too small. I think that you should work more on the scetch before shading it all out, as most of these problems should have been visible too then. You say you used many help-lines; well, I think you need more (o:

A good kind of practice, that I've seen other people use: If you commute much, bring a pad of paper with you when you travel in a train or bus, and make little scetches of people around you; feet, faces, hands etc. This will help you get a good feel for the shape of the human body (o;

The shading work is good, though, and your Godfather's recognizable; I'm certain that with sufficient practice, and a bit better help than I can afford you, you'll be able to do stunning work. Also, it's a clear improvement over the last one.

I think you are getting quite good, I like the shading and the detail you have put in around the eyes. A bit more practice and I think you'll be producing some professional portraits, well done +7

Nice piece.
Nice shading and amazing lines.
maybe you could make a little background but nice portrait anyway.

this is a good work.

i think it´s in the midle betwen a realistic and a expresionist portrait.
i don´t know which one it´s your choice.
if you want make it more real, check the mouth (brando have an odd mouth but this have some problem) and the two eyes they look to plain (2-D), the left one have the same size of the right it should be smaller because they are not viewed from the front (it`s a 3/4 portrait). you can use more levels of shadows.

if you want to make an expresionist portrait maby you can work out another (maby stronger) trace.

but anyway this is a fine work, and you are in the way to make your work better.
keep them coming.

Its a very admirable drawing, faces are very hard to get right even from photos. I think you are wise to practice your observation drawing, I have found it is one of the most important things to do if you want to improve, especially with anatomy. The eyes mabye needed a bit more highlight or shine in them, but it looks good otherwise

+7 from me
i like it

Overall still looks flat. Maybe you should add some shadow at the right side f the face (behind the nose) to give more depth