from what I can see, smash counts when u miss a direct hit. Like a bomb landed on the side and it dealt smash dmg to a unit near it.
Hit is basically a direct Hit from the front.
Guard is hit to their shield and the damage is relatively lower than hit and smash.
Critical is from the back. Basically it should be 1.5x or a higher multiplier of the damage(I am not 100% sure on the multiplier)
Crash is... I never had one @_@ Usually I just see it from teammates.