To believe in Allah is not enough to be classified in a muslim. A person who believes in Allah but does not submit, is the worst among people. Is a munafiq a person who believes in Allah and 6 pillars in Imaan but does not, thus refuses, to submit (5 pillars of arkaan + hadith + sunnah etc.) is the worst of all people ?
Is to believe in Allah is not enough ? The reason I ask is because you hear some people say that whoever believes in allah is a muslim or somehting along those lines

The example that was given was the ibliis. Ibliis believes in allah, for he made a duca to alah (to be allowed to live untill qiyamah), but he refused to submit. ??