you've got a stray pixel near his left leg.

I agree with your points; I have the problem of crooked lines in nearly every piece I do; I have heard of "jaggies" and their effects though but it's the same with Anti Aliasing; I know what it is but I just can't seem to execute it correctly. This piece is far from finished I hope to do some more work on it and use it as a learning experience. Thanks for your crit it really helps.

The main problem here is the incredibly shaky outlines. Tyranitar has a very smooth, almost metallic sort of armor, but with the outlines being as crooked as they are here it makes him look highly unstable. You may also want to look into using black outlines to give it more depth; you don't have to do this but the end result looks far nicer.

The shading looks very angular and sloppy; I recommend curving it. They could be placed a bit better (for example, the highlight on the tail is unnecessary), but otherwise they're acceptable.

It takes a lot of effort to make such a big piece, though, so kudos.