Most Painful Drug You've Snooted, Railed, Racked or Vacumed Up with your Nose
Pain is a perception, so its based on your own opinion.
Personally my worst snorting experience was with a flexeril. I crushed up one of the yellow 10mg, powdered it sufficiently and made myself a nice line. i rolled up my bill and took a deep breath, exhaled and then began to snort, after a second i was taken off guard... stopped snorting and just held still for a second. I coughed a few times to get the powder out of my wind pipe (idk how it got there) and attempted to snort the rest of the line. I ended up having to take another break to cough, clear my throat and finish the line. The drip was bad, but not like good MDMA or Xanax.