One of the best du’aa’s that may be recited on Laylat al-Qadr is that which the Prophet (peace and blessings of Allaah be upon him) taught to ‘Aa’ishah (may Allaah be pleased with her).
Al-Tirmidhi narrated, and classed the report as saheeh, that ‘Aa’ishah said:
“I said, ‘O Messenger of Allaah, if I know which night is Laylat al-Qadr, what should I say on that night?’
He said, ‘Say: Allaahumma innaka ‘afuwwun tuhibb al-‘afwa fa’affu ‘anni (O Allaah, You are forgiving and You love forgiveness, so forgive me).”

May Allah accept our fasts.
Ameen!