These are all really nice cover designs with good compositions.
So I'm feeling very pained as I bring up the forthcoming "but" after you clearly put work and thought into these...but...
None of them tells the viewer what the comic is about, so I wouldn't pick any of these (sorry!). I think maybe you're over-thinking this a bit.
I went and had a little look through the first pages of your comic, and here are the key points I think a cover needs to sell:
- This is a comic about an equally matched Superhero and Supervillain with basically opposing powersets. She's light as a feather and can fly, he has a gadget for everything.
- She's no-nonsense and idealistic, he's vain and arrogant, and the interplay between them is fun!
- It has an action-packed, wacky and comedic tone, focused on likeable characters.
So, to me, this should:
- Show two characters and make them look like they're equals (helps the audience understand that "They're both a Kilogram" refers to these two.)
- Have them fighting or arguing because their antagonism towards each other is the fun unique selling point.
- If possible show the contrast between them, like she can fly and is a classic superhero type, he's a villain with gadgets; that's fun and cool.
I'm not going to give a ton of example ideas because I think you can come up with something better yourself (you know your characters and style better than I do) but to illustrate, I think if you have both the characters currently looking like they're in a fight or a tense situation, and just show it literally, like on one of these, she's flying in to punch him and he's aiming a weird gadget gun at her and holding a ton of wacky gadgets like "there's more where that came from!" kind of feeling. Or another, she's grabbed him and is holding him up high in the sky, above the clouds, but he's holding a gun or something and a control for some sort of machine- what is it?! A bomb!? Tension!

The cover scenario doesn't have to be complicated or metaphorical, because you already have a great, simple thing to sell: Superhero is frustrated because this cocky-ass supervillain loves to tease her for her inability to stop him. She can fly (awesome), he has gadgets (also awesome). See what you can come up with to get that across. Make sure both of their faces are visible so we can see the emotional interplay between them; the rivalry between these interesting characters is a big point of appeal.