One of the greatest ways of erasing major sins is via the door of repentance that is found beneath the feet of your mother and father.
Abdullah Ibn Abbas (Ra) said I do not know of any good deed on the face of the earth. That is dearer to Allah Almighty than being good to your mother. And that is why Imam Ahmad ibn Hanbal (rah) and other said erases even major sins.
Five things to honouring deceased parents:
Prophet Muhammed (saw) Making dua for them and asking Allah Almighty to erase their sins. Carrying out their last wishes after they have died, honouring their friends that they used to love, love, taking care of those ties of , Family Ties that you have because of them.