Here are the common things I've noticed in the posts on this issue:ġ) This seems to happen on a second play through for all the posters who have mentioned it. It was 4/5 fighters at the time, and when I defeated Vasilis, it was still 4/5. I finished the level 50 Arena fight for the first time when I was level 43 or 44. I completed every fight in a reasonable period of time and I had not completed the main story when I realized it wouldn't complete. I have played through the main family quest line twice and at no point did I run into any of the Arena fighters outside of the Arena.

I would really like to know which Arena fighter they are talking about.