Critically Conditioned (Charge Rifle)

is one of the many challenges in Titanfall.

I'm fairly sure that rodeo hits using the charge rifle count as critical (Note: This only counts as a critical hit if the titan you are rodeoing has lost its shields). No splash damage to worry about.

If you have trouble getting the Titan's shields down while you're on top of it, consider throwing an Arc Grenade while rodeoing. This will hurt you for 50% of your health but will take down the Titan's shields as well, allowing you to charge the rifle and gain point towards the challenge.

This is misleading, as it is far easier to charge and hit red areas from a distance.