  In this letter we point out that the Lindblad spectrum of a quantum many-body
system displays a segment structure and exhibits two different energy scales in
the strong dissipation regime. One energy scale determines the separation
between different segments, being proportional to the dissipation strength, and
the other energy scale determines the broadening of each segment, being
inversely proportional to the dissipation strength. Ultilizing a relation
between the dynamics of the second R\'enyi entropy and the Lindblad spectrum,
we show that these two energy scales respectively determine the short- and the
long-time dynamics of the second R\'enyi entropy starting from a generic
initial state. This gives rise to opposite behaviors, that is, as the
dissipation strength increases, the short-time dynamics becomes faster and the
long-time dynamics becomes slower. We also interpret the quantum Zeno effect as
specific initial states that only occupy the Lindblad spectrum around zero, for
which only the broadening energy scale of the Lindblad spectrum matters and
gives rise to suppressed dynamics with stronger dissipation. We illustrate our
theory with two concrete models that can be experimentally verified.
