Phenol is less acidic than:

Phenol is less acidic than o-nitrophenol because the nitro group is electron-withdrawing, stabilizing the phenoxide ion through resonance and inductive effects, thus increasing acidity. In contrast, p-methoxyphenol has an electron-donating group that decreases acidity, and alcohols (2-methylpropanol and 2,2-dimethylpentanol) are less acidic than phenol due to lack of resonance stabilization of the conjugate base.