It's a minor thing, but also probably easy to implement. I just think it would be helpful to have a visual cue that marks a monster as a cheater. Something that can be seen before engaging it in combat. My idea is to have a symbol on the ground under their feet. Perhaps a simple starburst shape. I just think it's only fair for players to know what they're getting into.
Additionally, maybe a notification can come up (similarly to Wysteria during the Tournament), especially for new players or first timers questing within a particular dungeon or world for the first time.