Jazza already pointed out some trouble in composition, and mentioned making the background with a more painted feel. I thought I'd add on that and say that colour and composition largely impacts where our vision is guided.
Large areas of vivid colours are attention hogs, while dimmer tones are more harmonic and sort of "blend in". In this case, Pantheon and Leonas red and yellow shields respectively, attract a lot of attention; Vi is more dimmed down, and then sort of disappears in the composition. Similarly, the strong movement from Vi punching Panth attracts a lot of attention to the movement itself, rather than the character doing it. I'd suggest reading up on composition, and how to use it to make illustrations more clear.
Of course this is all nitpicking, great work on everything else!