A highly accurate and lethal pistol. The Carnifex is a favored sidearm of mercenary leaders and Eclipse mercenary tech specialists. An expensive but powerful weapon, its marketing materials feature a charging krogan with the slogan "Don't you wish Carnifex was at your side?"
The Carnifex is a powerful weapon for its category. On Bronze difficulty, it can kill any unprotected enemy with a headshot. Shielded organic enemies require two or three hits. With multiple weapon damage upgrades, it can retain the same stats on higher difficulties, though one more shot may be required for tougher enemies. On Gold, only through an Infiltrator's Tactical Cloak damage bonus can players one shot Assault Troopers or Guardians. Otherwise, it requires at least two shots to the head to kill unshielded enemies, and at least 3 to kill shielded enemies.
Combining the Carnifex with Stasis makes for a potent combination. With sufficient power duration bonuses, Stasis can hold an enemy in place long enough to put as many headshots as necessary to kill the intended target. This is particularly useful against Phantoms, as they are very dangerous at close range but only require a couple of headshots to kill.
The Carnifex is a good weapon for the Vanguard class to use, as its relatively low weight and high accuracy and damage allows the Vanguard's powers to recharge quickly as well as having the bonus of a high-damage weapon.
The Carnifex is very useful when equipped with the Piercing Mod as it allows for much easier performance of headshots on Guardians, which is an important consideration on higher difficulties. This mod also helps speed up killing enemies with massive amounts of base armor (such as Atlases) and allows you to shoot enemies out of thin cover simply by shooting their cover.
Equipping the scope is inadvisable, as the gun is pin-point accurate in cover, and extremely accurate out of cover, even at range. Only at 10-15 meters out and further does accuracy become a mild issue when shooting out of cover.
Used in tandem with Overload or Energy Drain, you can strip the shields of most infantry in one go, then with one well-placed headshot, subsequently kill weaker infantry.
Adrenaline Rush is an effective means of increasing damage for the Carnifex. Since it lasts 5-6.8 seconds and does 50-70% extra damage, one can fire off at least 1 entire clip of ammunition before losing this bonus, compared to 2 or 3 shots from Tactical Cloak. It may not affect how many shots are needed to kill shielded enemies, however. Consider teaming up with somebody with Overload to pick enemies off.
In an update, the Carnifex had its weight increased from 50 to 70, potentially making it less viable for power intensive classes.