  Observables sensitive to top quark polarization are important for
characterizing or even discovering new physics. The most powerful spin analyzer
in top decay is the down-type fermion from the W, which in the case of leptonic
decay allows for very clean measurements. However, in many applications it is
useful to measure the polarization of hadronically decaying top quarks. Usually
it is assumed that at most 50% of the spin analyzing power can be recovered in
this case. This paper introduces a simple and truly optimal hadronic spin
analyzer, with a power of 64% at leading-order. The improvement is demonstrated
to be robust at next-to-leading order, and in a handful of simulated
measurements including the spins and spin correlations of boosted top quarks
from multi-TeV top-antitop resonances, the spins of semi-boosted tops from
chiral stop decays, and the potentially CP-violating spin correlations induced
in continuum top pairs by color dipole operators. For the boosted studies, we
explore jet substructure techniques that exhibit improved mapping between
subjets and quarks.
