In this paper, we study the existence of unavoidable 2-edge-colored patterns in edge-colorings of the complete graph. We are interested in how these patterns change as the densities of the color classes change. A graph is called balanceable if it can be found, with half its edges in one color and half of them in the other, in any 2-edge-coloring of Kn with sufficiently many edges in each color class and n large enough. The balancing number bal(n,G) of a balanceable graph G is the maximum number m of edges such that there is a coloring of Kn with m edges in one color class without having a balanced copy of G. Equivalently, any 2-edge-coloring of Kn with more than bal(n,G) edges in each color contains a balanced copy of G. Graphs with constant (not depending on n) balancing number have been previously characterized. We give a new proof of such characterization that allows us not only to understand in a deeper way the structure of the graphs with constant balancing number but also to show that bal(n,G) is quadratic on the number of edges of G, a bound that differs substantially from the previous known that was exponential.