Ask my younger son’s first wife. She’s an expert on getting into the lowest possible credit scores. 
I’m guessing bankruptcies help drive it down as well.
Just WAGing here, but I’m thinking you’ll need all of these.
Foreclosures
Repossessions
Bankruptcy, maybe plural.
Years of 90 day past due payments on accounts.
Accounts in collection.
Maybe piss on the Experian CEO’s shoes for good measure.
Wife’s a banker, and she watches our scores like a hawk. She also sets up loan/credit scenarios* for the kids to ensure they enter adulthood with high scores. As a result, the whole family’s in the 800’s, wife’s is 840 (I asked her mine and she said close, but a little lower).
*Gets and pays cards and loans the kids really don’t need, just to establish their credit history. She says it’s incredibly important for their future, and that China isn’t the only country with a “Social Credit System”. Ours is handled by corporations instead of government.
Once mine was a perfect 850 on Wells Fargo investment site. Now it’s at 815 which is still excellent. I bought a car but paid off all my credit cards. There is no understanding it for me.
Mine is 855 out of 900. It was 867 but dropped in March. No clue why.