How many unpaired electrons does a low spin Fe(II) complex have?

A low spin Fe(II) complex has 0 unpaired electrons. The Fe(II) ion has 6 d electrons, and in a low spin complex, the ligand field splitting is large enough that it's energetically favorable for electrons to pair up in the lower energy d orbitals before occupying the higher energy ones. Therefore, all 6 d electrons are paired, resulting in no unpaired electrons.