Hmm… that’s a good question. My answers are gonna be a bit biased for factors outside of the game, so take that into account…
Best state, personally, was probably around the time Doomfist released in OW1. One of my favorite character drops, had a lot of my friends playing, community felt hype to be around because of everyone being like “OMG he’s actually real and he’s cool af!” - I rewatch the scene in his hero cinematic where he rips out Tracer’s accelerator and makes her disappear fairly often. 
Worst state is a close tie between OW2s launch and OW2 season 14 (or whenever Hazard dropped). OW2s launch was something to get used to, there was so much hate flooding in–and for good reason. All the systems it introduced, going f2p, launching with no PvE or story of any kind when that was the cited reason to send OW1 into maintenance… I definitely get why everyone was so angry. Support was brutal to play at the time, too.
S14 is right there with it because it’s, so far, the only burnout I’ve had on OW2. There were some outside factors like the drop of Rivals and personal stuff, but the season was just… empty. I didn’t much care for the theme, the mythic, the balance changes (as few as there were), and it was just… boring. I think I logged on to play a few games of Hazard because he was kinda fun, but that was it.