Which anions are more stable than the acetate ion $\mathrm{CH}{}_3\mathrm{COO}{}^{-}$ in water?

The stability of a carboxylate follows the acidity of the parent acid. $\mathrm{Cl}$ and $\mathrm{CF}{}_3$ withdraw electrons (-I) and formate lacks a +I alkyl group, so these three are more stable. The tert-butyl group is a stronger +I group than methyl and destabilises the anion.