Oh brother.on this forum, I have never come across 'sinfully' being used to mean 'very' or 'somewhat' or whatever meaning you were trying to convey
Here's just a sample:
https://www.baptistboard.com/threads/bad-grammar-in-the-esv.37187/post-978411
Rippon: "The ESV was just a dusted-off RSV . The 'revisers' didn't do much work . The syntax is sinfully poor."
https://www.baptistboard.com/threads/chior-robes.51875/post-1289909
Joshua Rhodes: choir robes are "too hot" and "ugly as sin".
