Hello,

I thought about a crazy animation where the character does a special attack when the next damage is an accurate one (due to a critical)

For example, when an engineer attack is critic, a high voltage super lighting would struck the target dealing a critical damage.
For commando, he would take out a grenade and shoots it at the target, dealing a critical damage.
For operative, a mine would explode just beneath the target, stunning it, and dealing a little more damage than normal.

We can do same with dodging.

An engineer would bend down.
A commando would skip it by sliding to the right.
An operative would step back to avoid the shot.

And a dodge can't happen at the same time as a critical shot.