one thing is not using black outline, another is to not have a dark enough outline
on the porygon2 pixel over the lover shade is to thin, try widen it a little
your revamps need more contrast in the colors
on the fusions the leafs on the doduo-weepinbel has a to fast shift of shades delete the lightest one and i think it would be better, also the leaf itself doesnt look that much like the leafs of weepinbell
I really like the pixel overs and the revamps, but you should add a bit of black outline. It looks weird since you can't see the outline clearly. You can add a darker shade of the color as the outline if you don't like using black outline. On the first mix, the head on the right, the lips need on the outline, not inside.