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.