Lets say you have the fortune that after all attack dice has been modified or re-rolled by the attacking opponent player. And he has only managed to secure one attack dice witth a Crit.

Can you nullify the effect of any upgrade card of his (say ACM, APT or XX-9) with your Evade defence token, If you have Mon Mothma, by making him re-roll the one die he has a crit on and it ends up with a blank or non Crit result???

Roll Attack Dice.
Attack Modifies Attack Dice (Including spending ACC to nullify defense tokens)

Defender Spends Defence Tokens.

Scatter and Evade take place immediately .

Determine Critical Effect

Contain takes effect here.

Determine how much Damage

Brace takes effect here.

Apply Damage 1 point at a time.

Redirect takes effect here.

....

So, attacker rolls 4 dice. Blank, Blank, Acc, Crit.

Spends the ACC to nullify the Scatter Token.

Then, when you get to your option to spend the tokens, you choose Evade , and he rerolls the Crit. It becomes a HIT.

Now, when you get to the next step - Determine Criticals... There is no critical .

Problem Solved. Its just a hit.