On the Day of Judgement, nothing will weigh heavier than the testimony of faith: ash-hadu an la ilaha illa Allah wa ash-hadu anna Muhammadan rasulullah. Even 99 scrolls of bad deeds will be outweighed by it.
Narrated ‘Abdullah bin ‘Amr bin Al-‘As:
The Messenger of Allah (ﷺ) said: “Indeed Allah will distinguish a man from my Ummah before all of creation on the Day of Judgement. Ninety-nine scrolls will be laid out for him, each scroll is as far as the eye can see, then He will say: ‘Do you deny any of this? Have those who recorded this wronged you?’ He will say: ‘No, O Lord!’ He will say: Do you have an excuse?’ He will say: ‘No, O Lord!’ So He will say: ‘Rather you have a good deed with us, so you shall not be wronged today.” Then He will bring out a card (Bitaqah); on it will be: “I testify to La Ilaha Illallah, and I testify that Muhammad is His servant and Messenger.” He will say: ‘Bring your scales.’ He will say: ‘O Lord! What good is this card next to these scrolls?’ He will say: ‘You shall not be wronged.’ He said: ‘The scrolls will be put on a pan (of the scale), and the card on (the other) pan: the scrolls will be light, and the card will be heavy, nothing is heavier than the Name of Allah.'”