  We demonstrate through first-principles calculations applied to the
K$_{3}$NiO$_{2}$ crystal that a structural phase transition from an achiral to
a chiral phase can be mediated by a degenerate soft phonon mode and controlled
by pressure and epitaxial strain. Breaking such degeneracy with an electric
field generates a competition between enantiomorphic, polar, and orthorhombic
displacements. Originated by the interaction between spontaneous chiral and
induced polar and axial modes, an optimal parameter window for converting the
handedness of the system into its opposite kind is observed.
