Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh

There is nothing called the curse or the spell of such a person will get me throughout the whole of my life. There is still mercy of Allah who stated that He forgives all sins except associating partners with Him. I suggest you do better to your father who is deceased by doing two things:

1) let him feel tranquil by being a sincere and good Muslim. Your righteousness will count at the scale of your dad’s good deeds.

2) Try to do a running charity for your dad by, for example, buying Quran and putting it at mosques or digging a well and dedicating it for his soul.

You can moreover do good to those whom your father used to love most. It is a part of being dutiful to him even after death. Ibn `Umar reported that the Messenger of Allah (may Allah bless him and grant him peace) said, “The strongest form of dutifulness is when a man maintains relations with the people his father loved.”  (Al-Bukhari, al-Adab al-Mufrad: 41)

Almighty Allah knows best.