Bearzone!
Really hard to know... lots of weird stuff on Arena Battle. A hacker's paradise...script user's drea...
Well you will realize it's a mod user after the result. If he has the same stats or much higher stats than you and the opponent has just barely started to use his uniques (60lvl. below) it is a mod user. By experience you will know that you get more resources the same time collecting more experience points at a certain stage. In other words you are leveling up while collecting resources.
At normal playing hundreds of million damage is achievable at level 100+ of a character. In this case (lvl 60) is achievable only if you don't play and buy resources with money. And I mean a lot of it (large sum). Would you believe that 😅