The most basic things that determine how many G's a plane can pull are:
1. The strength of the airframe (particularly the wing).
2. The flutter resistance of the airframe.
3. How fast the plane is going.
4. The maximum lift coefficient of the wing.
The number of G's is just the ratio of the lift force to the weight.
The lift force is proportional to the wing area, the coefficient of lift and the square of the airspeed.

A special case is a flying wing in which the mass (load) distribution matches the lift distribution. Such a wing has no bending forces, no matter how many G's are bening pulled. It will not break due to spanwise bending.