One of the cheapest things to do in
Final Fantasy games is to use a Phoenix Down on an
undead enemy for
instant death. Yes, you heard me. Just as it can revive fallen characters, it can do likewise to
the walking dead -- but instead of bringing them
new life, it totally negates their
existance. This even works on various
boss enemies.
A few bosses in FF games I've found to be susceptible to this cheap as hell but useful tactic: the Phantom Train of FFVI, Gerogero and Abadon of FFVIII, and Soulcage in FFIX.