When I look in my character record, the most powerful enemiy I defeated is listed as Elder Wolf. Yet I killed the sky dragon, undead Raedric, Fampyres and I guess many more stronger enemies...

Maybe it's just that char. Check other party members.

I'm soloing.

I am on the final map now (with Thaos), only to get there I killed shadow drakes and Adra animats. My new strongest enemy defeated according to stats: Animat. Wait, didn't I kill a whole group of those right after Act 2?... (Back then I also killed my first Adra animat in Cilaban...)