Ohh that sounds fun! :'D As my 6,75 projects went under some major changes through years (...even whole world settings), some of my OCs changed a lot :'D especially after I decided to make my OCs more human-like, not perfect beauty being c;
I think Adelinde have changed the most, as, well, I suppose only her hair colour and role in the story stayed the same XD so from aggresive and tsundere-ish she changed into soft, calm and warm girl, changed clothing to more mori-girl style inspired ones, and from a fox demon to a forest spirit.
Another one that changed a lot is Thomas, who went from a silent and serious pretty boy to a lazy, normal guy CX
Other OCs, including main character, changed as well, but my post is already way too long CX