Answer:
Octahedral
Explanation:
Recall that according to Valence Shell Electron Pair Repulsion Theory(VSEPR) the shape of a molecule is based on the number of electron pairs on the outermost shell of its central atom.
In BrF4^-, the bromine atom is surrounded by 6 electron pairs. Four bond pairs and two lone pairs. This means a total of six regions of electron density.
According to VSEPR Theory, BrF4^- has an octahedral electron geometry and its the molecular geometry will be square planar since it is of the type AX4E2.
An image of the BrF4^- is attached below.