What is a characters 'threat level'?

All characters have the basic RPG-esk explanations in not only their histories and such but also the capabilities of their characters. Such as strength or endurance or speed, you know, things like that. Well, in the world of DC as a role-play, NPCs will be fairly active. Not only that, but varied characters with different skills tend to do battle. Such as, for example, Batman and Superman. Who would win? Superman is physically superior, obviously. Batman is mentally superior, obviously. So how would to vastly different characters even consider doing battle? Their respective threat levels are the same. Which means they both have an equal chance of winning. A threat level takes EVERYTHING you can possibly do and ALL weaknesses you have, just everything, fuses it all together to form how much threat you pose to whomever you face. Superman and Batman would easily be a threat level of S, while say The GreenArrow and  The A.T.O.M. might be level A; these being just rough examples for the moment. Say Trigon is level EX, EX being something akin to 'beyond understanding'. It is a rank given to you to summarize everything you can and can not do as a whole to take down your enemy.