In the senate: major bipartisan bills on government transparency, ethics reform and nuclear proliferation.
In the Illinois Senate: Major reforms of the criminal justice systems, particularly regarding interrogations and the death penalty. Also several big education and health care bills.
Opposed the Iraq war in advance, for pretty much exactly the reasons it wound up going badly, not out of some reflexive antiwar stance (as he approved of the Afghan invasion.)
Worked his way up from a poor household run by a single mother to the editor of Harvard Law Review, a position that basically allowed him to do whatever he wanted in life going forward. Passed up a lot of easy money to go organize voting drives and to try and make things better in depressed urban communities.