He systematically used the power and influence of the presidency to project falsehoods, encourage division and violence, and potentially feed classified information illegally to foreign governments for his own personal gain.
He is currently on trial for bribing people to stay silent about his affairs during the 2016 election. He was previously found to have illegally taken classified documents back to his home in Florida and kept them after he was president, potentially to sell information. His son in law was given a career in the White House with no prior experience, and there is a huge paper trail to suggest that he got paid 2 billion by foreign governments for representing their interests during that time.
He’s like a corruption buffet, and he has openly stated he will retaliate against everyone he considers an enemy if he wins again.