If worse came to worse, he could always find dirt on Potter and extort him, or perhaps - if he really couldn't find another way - torture it out of him. Tom was reticent to take either of these paths though; Potter was far less objectionable than other wixen of his status, and had proven willing to negotiate. What's more, he'd aided Tom without expectation of reward when those cowardly Beauxbaton students had ambushed him, something Tom could hardly fathom but did, nonetheless, appreciate. No, if at all possible Tom would take the kinder road of compelling the truth out of Potter rather than forcing it.