What is the response to one who argues that whoever's good deeds outweigh their bad deeds will enter Paradise, thus justifying committing sins by relying on doing good deeds afterwards?

This statement is the epitome of arrogance and ignorance concerning Allah and His divine law. Its utterer does not know whether his good deeds will be accepted, or if Allah will observe his sins, hate him, and abandon him, thus not granting him success in obedience. The early Muslims (Salaf) said that one punishment for a sin is another sin that follows it, so a servant continues in sins until he cannot escape them. The righteous believer performs acts of obedience and fears that they may not be accepted or that he may be forsaken due to his sins.

A servant is ignorant of many of his sins; he may consider a minor sin to be major, and many acts of obedience may be mixed with hypocrisy or self-admiration. Ibn al-Qayyim said that what a servant does not know of his sins is more than what he knows, and his ignorance of them does not benefit him if he could have known them.

The texts of the Sunnah indicate that the Prophet, peace and blessings be upon him, used to seek refuge in Allah and seek His forgiveness for sins he knew and those he did not know, as in his saying, peace and blessings be upon him: "O Allah, I seek refuge in You from associating anything with You while I know, and I seek Your forgiveness for what I do not know," and "O Allah, forgive me my mistakes, my ignorance, my extravagance in my affairs, and what You know better than I do."

Therefore, one cannot enumerate his bad deeds to counterbalance them with good deeds, and obedience may not be accepted due to the imperfections mixed with it. The early Muslims (Salaf) were more concerned with the acceptance of a deed than with the deed itself. Thus, a Muslim must abandon sins, both major and minor, and perform as many acts of obedience as he can, remaining cautious thereafter. Such arrogant talk is from Satan, from whom Allah has warned us by saying: "So let not the worldly life delude you, and let not the deluder [Satan] delude you concerning Allah" (Quran 31:33).