The magnetic properties of a substance can be determined by examining its electron configuration: If it has unpaired electrons, then the substance is paramagnetic and if all electrons are paired, the substance is then diamagnetic.
KO2 is potassium superoxide. There is one unpaired electron in anti-bonding molecular orbital of superoxide. Potassium superoxide is paramagnetic due to the presence of unpaired electron.
NO2,ClO2,NO are odd electron species. Hence, they are paramagnetic.
The other are monoxide and dioxide contain paired electrons, so they will show diamagnetic behaviour.