Heh. That's the problem with the typical "No win" scenario. The players will invariably win it. Particularly if you don't use DM fiat and cheat the stats/rolls. It's just one of those things. The players will crit, the enemies will fail, etc.

As a player: I was in the Palladium Superhero RPG (Can't remember what it was called)... and the DM threw out these creatures that were supposed to be impossible for me to beat. Had some sort of energy shield, a lot of armor, a lot of SDC, etc. I was supposed to lose the fight so I could get kidnapped.

So this thing is rampaging through the city. My guy, randomly determined, had basically Hulk Powers/Sasquatch/Wolverine. Big, muscular, athletic, claws, etc.

So first round comes out and my Hero had charged into the fray. Off the cuff, just as Roleplaying "Color" I mention that I go for the target's head. Roll a natural 20.

DM is about to go "Well dip, you hurt it's shield but it's still powerful enough to slap you around" sort of thing when the co-DM for the campaign reminded him "... but it's a called shot to the head which bypasses all that main body SDC and shields..."

Suddenly "... oh... crap... roll damage..." I ended up maxing my damage out, with the crit multiplier it was enough to just destroy the head of this thing. Suddenly the whole campaign is off the rails and the guy is scrambling to figure out how to salvage it just because instead of saying:

"I attack."

I said:

"I charge at the guy and throw my whole body and momentum into slamming into the guy's head."