Find the odd one out.

$-\mathrm{OH},-\mathrm{OR}-,{\mathrm{NH}}_2,-\mathrm{COOH},-\mathrm{NHCOR}$

The atoms or substituent groups, which represent +R or -R electron displacement effects are as follows ;

$+\mathrm{R}\text{-effect: }-\text{ halogen, }-\mathrm{OH},-\mathrm{OR},-\mathrm{OCOR},-{\mathrm{NH}}_2$ $-\mathrm{NHR},-{\mathrm{NR}}_2,-\mathrm{NHCOR}$

$-\mathrm{R}\text{-effect; }-\mathrm{COOH},-\mathrm{CHO},>\mathrm{C}==\mathrm{O},-\mathrm{CN},-{\mathrm{NO}}_2$

Thus, -COOH is a - R effect showing group while other show +R effect.