Royal Guard Defender: These are the toughest non-Heavy units in the game in terms of durability, able to take around 8-10 shots from an Assault Rifle. Headshots still kill them in one hit, however, meaning that they are the best way to dispatch these tough units. Like the Royal Guard Assaulter, they use the P416, allowing them greater accuracy and firepower than their regular counterparts.
The Royal Guard Defenders are more powerful than the Royal Army Defenders. They still need a normal Takedown, however; the Guard Defenders won't die if you throw a knife after them (The Knife Throw Takedown will kill him). A well placed knife thrown in his head will kill him.