Welcome to Gaia! ::

I really like the way the body is drawn on the first one up until the crotch; I think for what you're going for his legs should be more dynamic, and unless you want to draw a fullbody with like super pointy superman feet and straight legs (which would be cool) the part of his legs that you're showing here should be more dynamic

For the second drawing I think you should take the fabric into account more
Right now it looks like everything is made out of t-shirt material so I'd take more chances with folds and texture (and use yourself as a ref)
Also keep in mind that with crossed arms you have to be careful. His left arm looks like it disappears into nothing and, if he's a villain, I would personally choose to show his hands more, like with arms crossed and gripping his arms, not having them shoved underneath, which conveys less confidence

You should also consider using a ballpoint pen (or pilot pen if you want super super clean lines) to make these look more finalized. It's also good because it kinda forces you to put something down and leave it there so we can bookmark what you need to work on better

Like all artists at your approximate skill level, the best thing you can do is look at real life. And try to make it so the parts of the picture you can't see still make sense as part of what you can see. I don't know if that makes sense to you, but it seemed to help my sister a lot.