The functional group that shows negative resonance effect is:

The resonance effect definition can be given as a chemical phenomenon, observed in the characteristic compounds containing double bonds in the organic compounds. The organic compounds have these double bonds in the structures and have the overlapping of the p-orbitals, usually on the two adjacent sides of carbon atoms.

Negative Resonance Effect: The Negative resonance effect happens when the groups withdraw the electrons from the other molecules by the delocalisation process. Usually, the groups are denoted either by -R or -M. The molecular electron density is said to decrease in this process. The negative resonance effect examples are, $C = O, - COOH, - C ≡ N$ and $- {NO}_{2}$.

$- COOH$ shows $– R$ effect, while rest $3$ groups shows $+ R$ effect via lone pair.