Impossible to answer.
First, are you talking ‘most debt in total dollars or pence or drachmas or rubles’? As in – total amount owed?
Or are you talking “most debt with respect to percentage of income”? As in, I made $100/week but I owe $95/week -
And are you talking 2018 dollars or are you asking about people in history? Andrew Carnegie owed a lot of money in 1900 – but dollars were worth a different amount then.
And are you talking about people/humans? Or are you throwing corporations into the mix?
As asked, the question cannot be answered.