Such a person is an imbecile. Allah told us not to commit kufr. There are
those who commit kufr!
Likewise, Allah has asked us not to divide. It’s not mentioned in the Qur’an that we won’t be divided. Division and differences among this umrah is inevitable to which history bears witness and so do the texts of the sunnah of our Prophet salla Allahu aliaihi wa sallam.
Whoever rejects the authentic hadiths of the prophet salla Allahu aliaihi wa sallam is a disbeliever as Allah said that he (prophet) does not speak of his own desire.
Kindly refer to the following link(s):
https://islamqa.info/en/115125

What is the ruling on someone who rejects the Hadith about 73 sects saying that Allah has asked us not to divide into sects Quoting Quran Ch42 -Vs14 and says we should avoid dividing into sects and that Quran should be given preference over Hadith in this regard as 73 sects will not happen and we should avoid getting divide into sects.

Commentary on Hadeeth | October 14, 2017 7:10 am
Previous

In a hadith of Abu Dawud which speaks of the causes of our destruction. It says loving the world and disliking death. Hubbut dunya wa karahiyatul mayt. What is the explanation of loving the world and hating death ? Does loving this dunya means doing haram things because of the love and leaving the obligatory things and being preoccupied with the dunya and disliking death in the way of Allah.
Next

Is this hadith authentic? is it Sahih or hasnan or weak or fabricated? Hadarth abbas (RA) reports that our prophet (SAW) said, whoever recites: “Jazallahu anna muhammadan sallallahu alaihi wasallam ma huva ahluhu” then indeed it will tire 70 angels for 1000 days(to record the reward).