  We calculate the relativistic six-meson scattering amplitude at low energy
within the framework of QCD-like theories with $n$ degenerate quark flavors at
next-to-leading order in the chiral counting. We discuss the cases of complex,
real and pseudo-real representations, i.e. with global symmetry and breaking
patterns $\text{SU}(n)\times\text{SU}(n)/\text{SU}(n)$ (extending the QCD
case), $\text{SU}(2n)/\text{SO}(2n)$, and $\text{SU}(2n)/\text{Sp}(2n)$. In
case of the one-particle-irreducible part, we obtain analytical expressions in
terms of 10 six-meson subamplitudes based on the flavor and group structures.
We extend on our previous results obtained within the framework of the
$\text{O}(N+1)/\text{O}(N)$ non-linear sigma model, with $N$ being the number
of meson flavors. This work allows for studying a number of properties of
six-particle amplitudes at one-loop level.
