If someone transform a character into a 0-dimensionnal being.

[QuasiYuri]

How the character can resist to this or cancel this?

 

[KaiokenBlueGT]

What?

 

[The_Smashor]

If they bring them down 3 dimentions being 6D or higher would work.

 

[Crimson_Azoth]

Uh, wat? Assuming that you mean just auto-making them 0-D, at that point, a character with Higher-Dimensional Manipulation autowins, and anyone with Time Manipulation could reverse the attack, and Attack Reflection could make life very difficult for the attacker.

I don't know why you would want to make someone 0-D. That just gives you incon at best.

 

[The_Smashor]

Unless you can damage lower dimentional beings and they can't damage higher dimentional beings.

 

[Andytrenom]

I think turning them into a 0-D should just be considered incap.

 

[Agnaa]

SCP-3143 can turn characters 0-D.

Other people have already given good answers. Causality manipulation could undo the attack, explicit resistance to it could have you resist it.