Which type of people will lose both the Dunya (the worldly life) and the Aakhirah (the Hereafter)?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

Losing both the Dunya and Aakhirah, which is the manifest loss – we seek refuge in Allah Almighty from this – will happen to some types of people, as it was confirmed, including the following:

1- Those who worshiped Allah with doubt and without certainty; Allah says (what means): {And of the people is he who worships Allah on an edge. If he is touched by good, he is reassured by it; but if he is struck by trial, he turns on his face [to the other direction]. He has lost [this] world and the Hereafter. That is what the manifest loss is.} [Quran 22: 11] Ibn Katheer said in his Tafseer (exegesis) about this verse, “Mujaahid, Qataadah, and others said: {on an edge} means in doubt. Others said that it meant on the edge, such as the edge or side of a mountain, i.e., (this person) enters Islam on the edge, and if he finds what he likes, he settles in it, and if not, then he leaves.”

Ibn ‘Aashoor said in At-Tahreer wat-Tanweer, “The loss of this world is because of the temptation that afflicted him, and the loss of the Hereafter is because of not benefiting from its reward that is expected for him.” 

2- The one who sells his Aakhirah for the sake of the Dunya of others; As-San'aani said in At-Tanweer Sharh Al-Jaami’ As-Sagheer, “Then shall I inform you of [what is] worse than that? ... the one who sold his Aakhirah with the Dunya of others; meaning for the sake of making others acquire the pleasures of the Dunya. This is the worst kind of all, because he lost his religion for something that does not benefit him at all, so he is the worst of the people in losing a deal; as he has lost both abodes.”

3- The one who is both poor in the Dunya and punished in the Aakhirah; As-San'aani also said in At-Tanweer, “The most miserable manifest loser is the one who is both poor in this worldly life and punished in the Hereafter; as he lost both worlds, and that is indeed the manifest loss.”

A poet once said (what means): "How excellent is religion and Dunya if they are both achieved, and how ugly is bankruptcy and disbelief if they are paired in a man."

Allah knows best.