According to Fajan's rule, smaller is the size of cation and more positive charge it has, stronger is the polarising power of that cation. Hence, that ion has a larger tendency to distort the electron cloud of anion. Hence, it has more tendency to formcovalent compound. The metal ions of FeF3,VF5,VF2 and TiF2 all belong to fourth period of periodic table. The metal ions exist as Fe3+,V5+,V2+ and Ti+2 respectively. The anions are same in all compounds V5+ has the smallest size and largest charge. So the molecule VF5 has largest covalent character.