Mg(OH)2 , is the odd one out among all the given compounds.
All other given compounds are amphoteric hydroxides except Mg(OH)2
An amphoteric substance is an ion or molecule able to act as an acid and as well as a base. Amphoteric oxides are compounds of oxygen which exhibits both acidic as well as basic characteristics. These oxides when reacting with acid undergoes a neutralization reaction to form water and salt. This exhibits the basic property of the compounds. Similarly reacts with the alkali to form salt and water, exhibiting acidic property.