A con artist does one more scam before he retires exposes dark secrets in his family well after his father dies unexpectedly.

Hi IvyEight6,
This is how I see it (using your own version of logline):

After his father’s unexpected death, a con artist decides to pull one last scam by exposing his family’s dark secrets.

However, there are confusing points you’ll have to address.
Questions:
1- How exposing his family’s dark secrets is a scam?
2- Why does he have to do his scam after his father dies? What is the relation between his father’s death with his scam decision?
3- What is he achieving by exposing his family’s dark secrets?
4- Was/Is anything stopping him from doing so?

You need to address all the above questions. Read your logline from the reader’s POV.
Re-write and we will see again.

I hope this helps.