  We study a class of tree-level ans\"atze for $2\to 2$ scalar and gauge boson
amplitudes inspired by stringy UV completions. These amplitudes manifest Regge
boundedness and are exponentially soft for fixed-angle high energy scattering,
but unitarity in the form of positive expandability of massive residues is a
nontrivial consistency condition. In particular, unitarity forces these
ans\"atze to include graviton exchange. In the context of gauge boson
scattering, we study gauge groups $SO(N)$ and $SU(N)$. In four dimensions, the
bound on the rank of the gauge group is $24$ for both groups, and occurs at the
maximum value of the gauge coupling $g_{YM}^2 = \frac{2M_s^2}{ M_P^2} $. In
integer dimensions $ 5\leq D \leq 10$ , we find evidence that the maximum
allowed allowed rank $r$ of the gauge group agrees with the swampland
conjecture $r < 26-D$. The bound is surprisingly identical for both $SU(N)$ and
$SO(N)$ in integer spacetime dimensions. We also study the electroweak sector
of the standard model via $2 \to 2$ Higgs scattering and find interesting
constraints relating standard model couplings, the putative string scale, and
the Planck scale
