at this size everything you do with pixels has really little to do with what makes pixel art special. Of course it's possible to do pixel art pixel perfect at this resolution too.
However It rather seems to me like you are stuggling with proportions and angles.
Other mediums like pencils or digital painting lend themselves much better to practice angles, proportions and measurements than pixels, where you are always "off" (well not at this res, but at smaller res).
Maybe you should practice measurement and proportions via tons of sketches to be a lo more comfortable with it.
Here we have tons of problems in the spaces which have to do with getting him recognizable, like in the face.
FOrms and depth are also a problem, if you look at the chin and his staff 8skull-hand intersection)
might seems like a ton of tiny things, but all those tiny issues sum up and will cause trouble in the further process to get it right.