Not even a half accomplishment considering that there are still 5000 US soldiers in Iraq.
I was 20 in 2008, the first election I could vote in. I was reasonably politically aware at the time but still learning. One of my very basic litmus tests for being a decent, rational person is / was acceptance of gay marriage. I was quite surprised to find that Barack Obama, this liberal phenom who had become a household name overnight, was not publicly supporting such a cut-and-dry issue that would've been barely controversial among his constituency at the time. That was not the sole reason I didn't vote for him, but probably the jumping off point of being more skeptical of his candidacy. Of course, his change of opinion on gay marriage nearly mirrored opinion polls crossing the 50% mark, just like Clinton.
1. Gay marriage/rights 1.5 Pulling out of Iraq (half an accomplishment, because the US had no business being there in the first place)
ACA is a dud, because it does nothing to address the artificially inflated costs.
So, in 8 years, we traded gay marriage for insane massive surveillance and a 'recovery' in job growth in the gig economy. Is that a fair exchange? Maybe, for the LGBT community. To be fair, he did inherit a giant pile of shit in 2008, but to think of him as some accomplished or revolutionary leader is a mistake.
In the end, he's just another centrist status quo "liberal".