The stability of carbanion in the following1)          2) 3) 4)

As the % of S-character increases, spherical nature of hybridised orbital increases, closeness of electron cloud towards the nucleus increases, and hence Electronegativity of carbon increaseshence the stabilisation of -ve charge on carbon increases,-IE group increases the stability of carbanion+IE groups decreases the stability of carbanion.As the carbon chain length increases, Its +IE strength increases, hence the stability of carbanion decreases.