So every once in a while someone comes up with a 'most powerful ever' creature they modded, which is fun. Of course, there's always limitations on how powerful you can make a creature before it stops being 'fun' and starts being 'boring and stupid'. Anyone can make an unkillable creature by just making it have a single bodypart, fireproof, and bloodless, and anything with [SPEED:0] is basically a game-breaker.
This is where we pull out all the stops. I propose a tournament to push Dwarf Fortress modding to its absolute limit. Just how powerful can a creature be made before you start running into the limits of the system itself? This will be a monster-vs-monster tournament, in which everyone who partakes has to come up with a creature that can defeat the current champion in the arena.
There is one rule, however, and it is as follows: Like a diamond which can only be scratched by another diamond, the ultimate megabeast must be capable of being killed, but only by another instance of itself. A mirror match between two of the creatures must have a conclusion in order for the creature to qualify. (And no attempting to cheat by giving it a syndrome class that only it can exploit. I already thought of that, and it doesn't count.)
None of these creatures will be of any use in the actual game, but we should learn a good deal about modding in the process. It'll be fun to see what comes out!
So. Shall we begin? Who wants to start?