I understand it's unclear whether Sanders would be able to implement his policies in the first place -- due to staunch Congressional opposition from all Republicans and also (maybe, probably) some establishment Democrats. But I think Sanders could be unprecedentedly good on foreign policy, as he stands more strongly against American imperialism than any other candidate did. I think this would be great for the well-being of the rest of the world. As President, Sanders would likely have a sway over foreign policy, without needing so much support in Congress (as compared to domestic policy). Sanders might well get a lot of his anti-imperialist foreign policy implemented successfully. Obama promised better foreign policy, but after winning the election he mostly sold out and broke those promises. Sanders, by contrast, is constant in his left-wing ideology. Although this may be seen as a liability in some ways, specifically it's the most commonly given reason for why people see him as "too polarizing", it's a benefit to foreign policy because it means he would likely pursue his superior foreign policy insistently and not give in or sell out. American imperialism causes an extreme amount of suffering and injustice in many parts of the world -- a degree of suffering and injustice that is typically nightmarishly more extreme than almost anything that exists within America itself. Also, the number of people suffering outside America is vastly larger than the number of people suffering in America. Because of that, the suffering and injustice caused by American imperialism (which Sanders could likely greatly reduce) seems to outweigh the suffering and injustice that exists in America (which Sanders could well fail to greatly reduce). So, on consequentialist grounds (and even on some non-consequentialist grounds, like duties of global justice, human rights, etc.), so I think it's worth it to support Sanders.

He's also the only person still running who hasn't personally been accused of sexual assault.