अपि चेत्सुदुराचारो भजते मामनन्यभाक्। साधुरेव स मन्तव्यः सम्यग्व्यवसितो हि सः ॥

api chet su-durāchāro bhajate mām ananya-bhāk sādhur eva sa mantavyaḥ samyag vyavasito hi saḥ

Even if the most sinful worship Me, with un divided heart, he too must be accounted righteous, for he hath rightly resolved;

In plain words: Krishna says that even a person who has done very bad things should be seen as good if he now worships God with his whole heart. This is because he has made the right decision.