Is it possible to kill Elite Guards silently?

Solution 1:

Elite Guards are the first of a couple of different types of enemy that are immune to instant-kill quick-time-event attacks.

That said, you can "stun" them and then instant kill them with certain equipment:

• Caltrops (although they must walk over them)
• Spike Mines (again, they must walk over them)
• Smoke Bombs (only if upgraded with the "choking gas" ability)

You can outright kill them with:

• Upgraded terror darts (terror dart FTW!)
• Ravenous insects, although this can be somewhat attention-getting to other enemies in the area

You can also lure them into traps or drop environmental objects (ie, chandeliers) on them to kill them. Or you could terrorize nearby guards and get them to attack everything, including these guys. I don't believe they themselves can be terrorized, though.

Solution 2:

Elite guards must be disabled, a special status effect granted by poisonous smoke bombs and caltrops, before they can be killed silently. Often, it is easier to use distraction items to get past them, but that does not mean silent kills are un-doable.