  We consider the Cauchy problem for the generalized
Kadomtsev--Petviashvili--Burgers equation in 2D. This is one of the nonlinear
dispersive-dissipative type equations, which has a spatial anisotropic
dissipative term. Under some suitable regularity assumptions on the initial
data $u_{0}$, especially the condition $\partial_{x}^{-1}u_{0} \in
L^{1}(\mathbb{R}^{2})$, it is known that the solution to this problem decays at
the rate of $t^{-\frac{7}{4}}$ in the $L^{\infty}$-sense. In this paper, we
investigate the more detailed large time behavior of the solution and construct
the approximate formula for the solution at $t\to \infty$. Moreover, we obtain
a lower bound of the $L^{\infty}$-norm of the solution and prove that the decay
rate $t^{-\frac{7}{4}}$ of the solution given in the previous work to be
optimal.
