The little caveat in ICON combat rules was that, while combat could be quite lethal for an average character, tough characters became almost unbeatable. A really tough Klingon or Jem'Hadar, for instance, could whitstand phaser hits that would have vaporized any other humanoid.
Then again, this can be seen as another way to emulate what we saw on screen when Kirk punched a Gorn...
"The main difference between Trekkies and Manchester United fans is that Trekkies never trashed a train carriage. So why are the Trekkies the social outcasts?"
Terry Pratchett