He spent a lot of time in the senate with very little to show for it.

That's a common criticism, but I'm not sure it's fair. He's been one of a small handful of "voices in the wilderness" in Congress. It's probably hard to pass landmark legislation when you have fundamental disagreements with >95% of your colleagues about the direction the country is headed in. Looking back on his career, maybe he was just ahead of his time.

The bill to end support for Saudi Arabia in Yemen is a good example of this. He's been mostly consistent in opposing military intervention throughout his career, and finally managed to craft a bipartisan bill (thanks to a Republican's bugaboo about executive power), but even then, it languished without wide support until Saudi Arabia got sloppy with a bone saw.

So there's one success, and a recent one. I think the world is starting to prove Bernie Sanders right about a number of things. If he had started his career in the kind of political environment we have today, he might have been far more legislatively successful. Activist politicians have been much more successful in other times in our past.