Correct order of increasing covalent character is:
LiCl < BeCl2 < BCl3 < CCl4
All have Cl− as anions. No effect from their side.
Cations polarizing power:-
ϕLi = 1rLi ϕBe = 2rBe ϕB = 3rB ϕC = 4rc
As rc is least and its charge is highest.
Thus ϕc is highest. Thus, CCl4 is most covelent.
This is followed by ϕB , ϕBe and ϕLi
∴ The order is LiCl < BeCl2 < BCl3 < CCl4