[Kameron8]

if it was a 20% on crit to stun

with two attacks it isn't a 40% chance to stun Its a 28% chance to stun
Via binomial distribution the chance of a 20% stun happening after each failed attempt is
1 (28%) 2(36%) 3(48%) 4(59%) 5(67%) 6(73%) 7 (79%) 8 (83%)

This assumes 100% crit and hit chance

It's 36%, not 28.