It might also come down to too much AA for such small stuff.

Thanks for the advise, I'll watch out for that. :)

Consider working on contrast more: your pieces often have it too high or too low, and it makes them hardly readable.
For example, the jet`s cannons/missiles have almost exactly the same brightness as the background which makes them close to invisible. Blue background behind green skin is also a bad idea.
Conversely, Hulk`s eye and mouth and the watch`s arrows stand out too much.

Here are some thoughts on the hand (without any shape adjusting, although it`s needed IMO) and a tiny suggestion for the arrows:


Contrast is one of the key things in images that small.