CH would not fear the lion.
https://www.wired.com/2010/12/fear-brain-amygdala/
If the lion can supposedly close the said gap in 400 milliseconds, the CH can shoot 3 accurate gun shots during that time. It's highly likely that the human would be smart enough not only to dodge out of the way of the charging lion
while skillfully shooting it, lions aren't tanks. 3 shots to the head will likely kill it, if not stun it, if not, DEFINITELY slow down the 400 millisecond limit, meaning the human can fire more bullets into its head and end the 'fight'.
Besides, this is assuming the lion is the Flash and can accelerate nigh instantaneously to 50 mph from 10 meters.
https://www.youtube.com/watch?v=WzHG-ibZaKM
With bones 8 times denser than normal, a lion paw won't knock out the human in one go. (link's in the CH profile).
Also, CH's intelligence will understand lion behavior, and how it likes to go for the neck. Obviously, CH knows to protect that area should the lion comes close, and then CH can casually snap the lion's neck due to its lifting strength.