withholding of a loan guarantee, if a corrupt prosecutor wasn't fired.
https://www.rollingstone.com/politics/politics-news/biden-ukraine-prosecutor-trump-tweet-888662/
"Biden was one of the leaders of the effort to remove Shokin, and a month after Kasko’s resignation, he threatened to withhold American loan guarantees from Ukraine so long as Shokin was heading the prosecutor’s office. Christine Lagarde, the managing director of the International Monetary Fund, also threatened to withdraw financial support for Ukraine unless it cleaned up its corruption problem. Pretty much everyone recognized Shokin had to go, and a month later Ukrainian Parliament voted to remove him from office."