The more basic oxide is

Oxides of metals are basic in nature & oxides of nonmetals are acidic in nature whereas oxides of metalloids are amphoteric in nature.
Metallic character decreases as we move left to right in the periodic table so the basic nature of their oxides will also decrease. Therefore, alkali metals oxides are more basic than other groups.

Metallic character increases down the group in the periodic table so the basic nature of their oxides also increases.

Hence K₂O is more basic.