  In this paper, we derive a characterisation of negative scalar potentials,
$V<0$, in $d$-dimensional effective theories of quantum gravity. This is
achieved thanks to an Anti-Trans-Planckian Censorship Conjecture (ATCC),
inspired by a refined version of the TCC. The ATCC relies on the fact that in a
contracting universe, modes that become sub-Planckian in length violate the
validity of the effective theory. In the asymptotics of field space, we deduce
that $-V'/V \geq c_0$ when $V' \geq 0$. The rate $c_0 = 2/\sqrt{(d-1)(d-2)}$ is
successfully tested in several string compactifications for $d\geq 4$. In
addition, a new asymptotic condition, $V''/V \geq c_0^2$, is derived. By
extrapolation to anti-de Sitter solutions of radius $l$, we infer the existence
of a scalar whose mass should obey $m^2 l^2 \lesssim -2$. This property is
verified in many supersymmetric examples.
