While great, the boss fights in Deus Ex: Human Revolution drew the ire of fans who wanted to play stealthily.
While you can approach most of the game from a stealth/non-lethal standpoint, the boss fights require that you kill the enemy, and you really have to utilize some heavy firepower. So in this way, it was viewed as a definite design and pacing flaw.
But if you'd like to see a Deus Ex boss encounter where you can actually subdue your foe with a non-lethal takedown, you need to pick up that new DLC, "The Missing Link." It adds 5 hours of gameplay and finds protagonist Adam Jensen stripped of all his weapons and augmentations so obviously, stealth will be essential. And as for the boss; listen to what Eidos Montreal production coordinator Marc-Andre Dufort had to say:
"We have a boss battle at the end, but it's different from the main game boss battles. You can actually not kill the boss. You can do a non lethal takedown on him. And you can kill him from afar. You can even kill him without him seeing you. It's more of a bigger challenge than a standard boss fight like we have in many games."
What you may not know is that the boss fights in Human Revolution were actually outsourced to Grip Entertainment, and they admitted they weren't all that familiar with the Deus Ex universe. Our only question is: why would a studio outsource one of the most important components of a game?
Well, at least it still ruled (for the most part).
Related Game(s): Deus Ex: Human Revolution