2008, because at least there was a few months of fleeting hope where now I know this is nothing more than a brief remission.
I would argue that because of polarization, if Democrats win the GA runoffs, a 50-50 senate, a 224-211 ish House, and the Presidency would be more powerful than Obama's trifecta in 2008. We've already seen how powerful a narrow Republican trifecta was between 2016 and 2018, and since then, polarization has only gotten worse.
Only if they act on it. It's Democrats were talkin' about, not liberal/leftist Republicans.