If being totally honest, yes with a but.
All Presidents are war criminals, by a strict definition.
Reagan was a war criminal, but no buts necessary. His history is horrific, utterly despotic, in its inequities. He was a lunatic and enable lunatic passions.
Bush 43 was a war criminal, in that his military unnecessarily bombed Iraqi troops as they retreated and his actions fucked over the Kurds by pulling all resources on them after promising support.
Clinton was a war criminal, but he couldn't go into Rawanda due to domestic issues concerning the aftermath of Somalia. He bombed civilian targets trying to hit bin Laden. He authorized incursions into Kosovo.
Bush 45 was a war criminal, because duh. Every fucking action he took overseas fit into criminality. He may have been an unwitting moron or a decisive war criminal depending on your interpretations of his beliefs, but he led to hundreds of thousands of dead people regardless. Add in Guantanamo, extraordinary rendition, etc.
Obama was a war criminal, in drone strikes that hit civilian populations and his continuation of Bush's wars.
Trump, we hardly need to discuss.
And this ignores 90% of what these men did.
Sanders, if elected, would end up a war criminal by definition.
Honestly I think this is fairly true. Sanders would probably have an appropriate level of cynicism about the ability of American military force to create positive change, but he's just one man. The military-industrial complex is chock full of people who believe very earnestly that we have a responsibility to use our military force to create positive change, because that's the kind of person who spends forty years in the military and rises to general or whatever. I think Sanders would do much better at reining in the American military. But I think, if judged by the same standard, he'll probably end up a war criminal too. The boulder is too large.