  The electrocaloric effect (ECE), i.e., the reversible temperature change due
to the adiabatic variation of the electric field, is of great interest due to
its potential technological applications. Based on entropy arguments, we
present a new framework to attain giant ECE. Our findings are fourfold: $i$) we
employ the recently-proposed electric Gr\"uneisen parameter $\Gamma_E$ to
quantify the ECE and discuss its advantages over the existing so-called
electrocaloric strength; $ii$) prediction of giant caloric effects $close$ to
$any$ critical end point; $iii$) proposal of potential key-ingredients to
enhance the ECE; $iv$) demonstration of $\Gamma_E$ as a proper parameter to
probe quantum ferroelectricity in connection with the celebrated Barrett's
formula. Our findings enable us to interpret the recently-reported large ECE at
room-temperature in oxide multilayer capacitors [Nature 575, 468 (2019)],
paving thus the way for new venues in the field.
