four forces act on a point 2N.2N.2N.4N determine the equilibrant of the four forces
Forces are vectors.
They have magnitudes and directions.
You gave the magnitudes.
You did not give the directions.
Therefore the resultant has a magnitude somewhere between 2 and 10 N and some direction.
Without knowing the resultant vector, I am powerless to come up with an opposite vector equal in magnitude.