John 6:29 Jesus answered, “The work of God is this: to believe in the one he has sent.”
Ironically, the Catholic church is the master of legalism leaving its adherents in terror of fire and brimstone for not having made the grade in their own works that the Catholic church set up for them to do.
The Law can save no one and no replacement law that man sets up can save anyone either.
Only by throwing yourself on the mercy of the court, so to speak, and asking God for forgiveness can do that. And once He does, it's a done deal. He seals us with the Holy Spirit until the day of redemption. THAT's security.
Ironically, your argument isn't worth the cyberspace it is written on because the Catholic Church does not teach "fire and brimstone". It teaches that the greatest pain of hell will be the eternal loss of the joy of being in the presence of God. It took those kindly "reformers" to scare the children and peasants with something that horrible in this life.
INDEED.