Neither of the 1x images show up for me...
You said you worked on the troubled problems? Well they're still there, actually. Or it just seems like it. I should have gone into detail earlier. Keep in mind, you may be hearing some terms that are new to you. Don't worry, I'll explain.
First off, outlines are persistent everywhere. Everywhere. It's painful. But don't get rid of them just yet!
When I said there was a problem with the palette, I was addressing several problems at once, actually. Dark colors aren't dark enough--the shift from light to dark is actually not very noticeable overall (to me, at least)--and you have a lot of similar colors that, seeing how similar they are, could be gotten rid of. And anyway it's just a straight ramp from light to dark. No hue variation as far as I can tell. And considering this is a zombie game you could make things a bit darker, having most colors cold--at least the darks--or somewhere around there. I don't know. It depends on the type of atmosphere you want to give off. I'm presuming this is going to be somewhat humorous? Seems that way what with the caricatured players. And aforementioned palette.
You also have a poorly defined light-source. Seems to be coming from the left on the guy's hat, from the right on the zombie's brains, from
all directions on that woman's "hair". When the light-source is defined, albeit poorly, shapes seem to be pretty flat.
All I can give for now. There's certainly more.