Newton's first law establishes the following:
An object will remain at rest or with uniform rectilinear motion unless an external force acts on it.
Therefore, we have that a case contrary to Newton's first law is:
Unbalanced forces acting on an object at rest, cause the object to remain at rest.
It is false, because if the forces are unbalanced, then the object will not remain at rest because external forces act on the object.
Answer:
A situation that is contrary to Newton's first law of motion is:
An object at rest stays at rest as long as unbalanced forces act on it.
