Doing a combo of strafing, w tapping, and consistent aim, you can easily beat someone with a higher ping than yours. If they tried to crit-spam you, going back won't help, but rather pushing forward and hitting them back, or basically critting them back. They have advantages as well as disadvantages, over someone with low ping. Maybe I'll demonstrate with a video, if I didn't forget :p
Edit: and holding W when you get hit can reduce your knockback, regardless of what ping you have. Use that to your advantage too. :)