It's lookign good to me. The frames seem to be skipping a bit so I cannot really say how the animation looks, but ponytail is pretty noticeable. Perhaps look at Balmafula to get the idea of how it should swing? That could help.
I like his collar and belt, overall it's a solid concept, great work on that
For the Iron Giant's death pose, you might want to erase his eyes. You know, make it look like a hollow helmet. Right now he's just holdng his sword before him and lookin at you, not really working as a death pose I think
Since you said something about animating problems, so I went ahead and animated the scarfon forward walking more, since you didn't fo the first two frames. I tested some of Natsu in the game, and overall he looks real nice. Gotta admit I am liking this sprite
Natsu sprite realy came out well, after all the fixes since the first version. I like it a lot . Good job on the bac frames and its hair, came out WAY better than the first version! As to the portrait, it could use some better shading on the hair. You seem to have your own style on those, but it doesn't fit into FFT much, more like Disgaea style etc.
Yeah, white outline was a pain. Then again you need to notice that Kirito's design is mostly all black, with white outlines. It is hard to transist it into a FFT sheet, cause blacks will blend together. This white outline is mainly used to separate some blacks and make it look like it's not a big black lump. Feel free to do anything with it, it's just a concept I did long time ago, after I finised watching SAO