Q: How do you kill a man like "Scarecrow"? An elite soldier with the resources of the words most formidable super power, a fighting force vastly superior to any in the world, equimpment, technology and budget unparalleled.

A: You turn that asset, that amazing fighting force, the USA against "Scarecrow". Using the very latest in polylatex, document forgery and computer hacking, I would construct a disguise indistinguishable from the original Schofield. A latex mask far superior to any ever made, with documentation forged by the worlds best. I'd enter NORAD with Scofield's security clearance and hack into its top secret "echelon program", a computer program so advanced it is the first line of defence against any threat the USA may encounter. An advanced program capable of deciphering every transmission on the internet. This weapon is knowledge and while they have this program they have knowledge and no one else does. I'd kill several NORAD personnel, leave DNA evidence behind, hair and fingerprints. I'd intentionally be seen on camera. Then I'd disappear.
I'd broadcast the program over the Net making it useless then disappear. The country Scofield loves would do the rest. Hunting him relentlessly until he is no more.