This is Roper bringing you a complete 100% walkthrough of Hitman: Absolution. This video will get you the following challenges in level 19, Countdown:

Chameleon
Evidence Collector
Infiltrator
Suit Only
All Roads Lead to Dexter (Part 1 and Part 2)
Stay on Target 
Hazardous 
Axed 
It's Personal
Face to Face
Take Em Down Part 1
Take Em Down Part 2
Take Em Down Part 3