Look,
English is not my motherlanguage and I have to go to all kind of courses and classes to understand what an English person say.
By the time I learned this grammar tip that COULD/SHOULD + HAVE means regret I really didnt get it. After watching this hell of an episode, I just could say I learned it.
the time Bojack was explaining to Charlotte what he missed through years because of not choosing that life was heartbreaking and I, with the most ridiculous reasons, wanted Charlotte to get cut up in the moment and make it with Bojack. But as Bojack said: you will never get a happy ending,
by far I consider this episode the most hope breaking of all time