There are no sins that Allah doesn’t forgive if one repents and makes amends.
But if one dies that is a different story, Allah doesn’t not forgive ‘shirk’ – associating others with Allah – other than that, Allah may forgive.
But I wouldn’t take my chances, I would repent and make amends now.
If the sin is against others, I need to get forgiveness from the other parties I have oppressed.