* Nuclear disarmament (you know, what he ostensibly got his Nobel peace prize for)... yeah, that's firmly dead in the water.
* The big Muslim reconcilation (his big speech in Cairo in 2009)... post-Arab Spring, there's a lot of disillusionment in the Muslim world considering that actions haven't matched up to those words.
* Syria's chemical weapons, wherein Obama threatened heavy repercussions should Syria use them in its civil war. Said heavy repercussions turned out to be merely exporting those weapons and not even anything so hefty as extracting an admission of guilt or instituting a trial in the ICC or ICJ over their use.
* The Asian pivot, whose biggest practical effect has been to cause allies to question America's willingness to uphold its own commitments.
* The Russian "reset"... okay, this one is Putin's fault. :-)
You can argue that, in many respects, Obama is/was constrained by public opinion, but that's just the mark of the most common failure of politicians: the politicians whose names echo through history are not the ones who follow public opinion, but the ones who lead it.