Even the worst muslim to go in Jannah would be devoid of any kabaahat and marz of the heart. No one will fall into any futility.
لَّا يَسْمَعُونَ فِيهَا لَغْوًا إِلَّا سَلَامًا وَلَهُمْ رِزْقُهُمْ فِيهَا بُكْرَةً وَعَشِيًّا ﴿مريم: ٦٢
They will not hear anything absurd therein, but a word of peace, and there they will have their provision at morn and eve. (19: 62)
Does this person know something what Allaah Subhanahu Ta’ala doesn’t know of? naudhubillaah
There is a limit to jesting! The sirah of Muhammad Sallallaahu ‘Alayhi wa Sallam would help.