Ba(OH)2 can be neutralized by adding an acid to the solution. We can add HCl to produce:
Ba(OH)2 + 2HCl ===> BaCl2 + 2H2O ; producing a salt BaCl2 and water.
or we can add H2SO4 to produce:
Ba(OH)2 + H2SO4 ===> BaSO4 + 2H2O; producing a salt, BaSO4, and water.