It is mentioned in a Hadeeth from the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, that the Shaheed is forgiven at the first drop of his blood. Is the Shaheed forgiven for all of his sins, even major sins? May Allaah The Almighty reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

Shahaadah in the Cause of Allaah pardons all sins related to the rights of Allaah The Exalted. As for what relates to the rights of the created, like debts and such, then Shahaadah does not pardon that. This is because nothing can deny a person his rights or his retribution on the Day of Resurrection. Allaah The Almighty could, however, bestow favors upon the Shaheed who is bound to others from creation, so He could make them content with him as He wills.

Allaah Knows best.