We recently watched Who's Afraid of Virginia Woolf? (1966) in our movie club and I was going to mention Roman Polanski's Carnage, another film based on a play about two contentious couples, but it looks like we're not getting Carnage after all. So it goes. Though, with all respect for Carnage, it's probably a hushed whimper compared to the savage WAoVW.
I have yet to see a marriage on film as intense, biting and, well, crazy as portrayed by Liz Taylor and Richard Burton (really married at the time). This is one of my all-time favorites. Check it out.
Like Withnail & I this film would make a good drinking game...if you're looking to kill yourself.