A large coercive field (E_C) and ultrahigh piezoelectricity are essential for ferroelectrics used in high-drive electromechanical applications. The discovery of relaxor-PbTiO₃ crystals is a recent breakthrough; they currently afford the highest piezoelectricity, but usually with a low E_C. Such performance deterioration occurs because high piezoelectricity is interlinked with an easy polarization rotation, subsequently favoring a dipole switch under small fields. Therefore, the search for ferroelectrics with both a large E_C and ultrahigh piezoelectricity has become an imminent challenge. Herein, ternary Pb(Sc_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ crystals are reported, wherein the dispersed local heterogeneity comprises abundant tetragonal phases, affording a E_C of 8.2 kV/cm (greater than that of Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ by a factor of three) and ultrahigh piezoelectricity (d₃₃ = 2630 pC/N; d₁₅ = 490 pC/N). The observed E_C enhancement is the largest reported for ultrahigh-piezoelectric materials, providing a simple, practical, and universal route for improving functionalities in ferroelectrics with an atomic-level understanding.