Tree Amplitudes and Linearized SUSY Invariants in D=11 Supergravity

We exploit the tree level bosonic 4-particle scattering amplitudes in D=11 supergravity to construct the bosonic part of a linearized supersymmetry-, coordinate- and gauge-invariant. By differentiation, this invariant can be promoted to be the natural lowest (two-loop) order counterterm. Its existence implies that the perturbative supersymmetry does not protect this ultimate supergravity from infinities, given also the recently demonstrated divergence of its 4-graviton amplitude.