What could they have on him that would matter? Honestly?
I don't really buy this kompromat argument, even if it was some horrific sex tape it would just be "fake" or "fake news".
I think it's likely just the flattery and importance they give him, the strongman image he desires and he likes the way Russia is a dictatorship. I just think he likes their system.
But it wouldn't be a financial debt more likely some humiliating kompromat. That's Trump's biggest fear.
And Putin probably has plenty from Trump's visits there.