I'm not sure I understand the problem. That corner is beautiful compared to most. Corner bead isn't normally screwed, though, for the reason you've encountered--screws pull way to hard and cause deformation. Use drywall nails (gently) or narrow-crown staples (like for underlayment).
Be sure to keep the bead above the plane of the wall. In the photo, the top side has a slight recess where the edge of the other sheet terminates. Don't pull the bead down tight to that. I like to stand a carpenter's square on the wall surface and lap onto the bead. If the square doesn't have a slim gap under it, shift the bead flange on the adjacent wall face to make it so. Imagine pulling your taping knife down that wall later... you don't want it to scrape the flange.
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