In this work, we introduce the concept of a convex-power condensing mapping T with respect to another mapping S as a generalization of condensing and convex-power condensing mappings. Some fixed point theorems for the sum T + S with S is a strict contraction and T is convex-power condensing with respect to S are established. The cases where S is nonexpansive or expansive are also considered. Our fixed point results encompass the well known Sadovskii's fixed point theorem and a number of its generalizations. To show the usefulness and the applicability of our fixed point results we investigate the existence of mild solutions to a broad class of neutral differential equations.