Your question is vague. To be able to declare anyone a Kafir one must attain exact and clear statements of beliefs. Having said this to believe other humans are equal in status to the Prophets or better is clear misguidance and can be a reason for declaring a person Kafir.

For example, the Shiah sect has a belief that the 12 Imams are all protected from sin or what is known as "Ismah" (or “Masoom”). This belief also entails the belief that these personalities are chosen by Allah taala and it is obligatory to follow their commands. In this case one clearly sees that they have to all intents and purposes nullified the Finality of the Prophethood of the Messenger of Allah (peace and blessings be upon him) and this cannot be reconciled by arguing that these are only Imams and not Prophets, as once one has acknowledged the attributes that befit only a Prophet to other than a Prophet, it is irrelevant what name you give to that person. Such a person is a clear disbeliever; if anything his Kufr is an extreme form that Islamic Scholars have termed “Zandiqa.”

The great Scholar Shah Waliullah writes: “…or affirms that the Prophet (peace and blessings be upon him) is the Seal of the Prophethood, however, this means (according to the Shiah) that it is only impermissible for any person to be called a “prophet.” As for the essence of Prophethood namely, that a person be sent by Allah to the creation, whose obedience is necessary and is protected (masoom) from committing sins as well as persisting upon an error, then that is found in the Imams after the Prophet (peace and blessings be upon him), such a person is termed a Zandiq...” Al-Musawwa vol.2 p.109.