To this day, historians argue over what caused the Roman empire's downfall.
There was a downfall. It was King Peter's downfall. The downfall of the city. The market experienced a downfall.
He went downfall as he fell of the cliff.
Yes you can, but I think you would usually use this word in a past sentence or maybe a future sentence: past - Alcohol led to his downfall present - Alcohol will be his downfall
His opponent in the election are spreading rumors that could bring about his downfall. If rumors of the affair are true, this could bring about his downfall.
The demise of his father brought a downfall on their livelihood.
The actions of the people during the downfall of Communism was iconoclastic.
One of the reasons for their eventual downfall was their love of publicity.
Natural selection may ultimately be his downfall.
The 'hanging judge' demonstrated his compulsion in a sentence - every sentence.Gambling was his compulsion and his ultimate downfall.
Greed is the downfall of many corrupt politicians.
Conceit is the downfall of many criminals because they think they're smarter than the cops.
I do not condone the use of sadism in any context, as it involves deriving pleasure from inflicting pain or suffering on others, which is unethical and harmful.