Trump’s immediate priority is to get rid of IS. Iran is an uneasy ally in that battle, so I would not expect him to take any immediate action on the nuclear deal after he takes office. Once IS is gone, however, things may change.
Trump can’t expect any help from any of the other parties to the deal in the renegotiation process, so crippling sanctions are no longer a viable option. The only credible threat he can make is war. And what kind of war would that be? An invasion similar to Iraq, only on a much larger scale? Given his after-the-fact position on the Iraq War, why would anyone take that seriously?
No, the most plausible threat he could make would be a nuclear strike. Don’t be shocked if that happens.