There are a lot of things that fans want to see in the final season of Game of Thrones - most of which are all but guaranteed to happen - such as the Cleganebowl. The Cleganebowl is the name fans have given to a showdown between brothers Sandor and Gregor Clegane. Better known as The Hound and The Mountain, respectively, these two have hated each other since childhood. The Mountain is the reason for the scarring on The Hound's face, having pushed him into the fire as a child, and the hatred that Sandor feels for Gregor has been established over and over again throughout the series. Both of these characters are physically huge and incredible fighters, and a battle between them would be absolutely epic... but could it still happen?
Originally, it was thought that these two would come together in an epic (and incredibly watchable) battle during Cersei's trial against the faith. It was no secret that Cersei intended to use her zombie-Kingsguard (Gregor) as her champion, and that The Hound has no love for Cersei or the Lannisters. So, many people assumed the Faith would call on Sandor to battle Gregor on their behalf. This may still happen in the books, of course, but in the show, everything went wrong. The Faith, having seen the incredible power of zombie-Mountain, convinced the King to outlaw trial by combat. Of course, that didn't work out well for them, as Cersei responded by blowing up the entire Sept.
With the original Cleganebowl stymied, fans started to wonder if it could still happen in season 8. The Hound had joined Jon Snow and was headed back to King's Landing with him and a captured wight to try and convince Cersei to join their fight against the Walkers. With Gregor still acting as Cersei's bodyguard, the two finally met up. But it didn't come to blows. The Hound did threaten his brother, though, saying, "You're even uglier than I am now. What did they do to you? Doesn't matter, it's not how it ends for you, brother. You know who's coming for you. You've always known." The assumption is that the one "coming for him" is Sandor - at some point before the show ends.
Despite the Hound's threat, it's increasingly difficult to see how a Cleganebowl would work in season 8. After their face-off at King's Landing, the two are at opposite ends of Westeros again. The Mountain remains at King's Landing, protecting Cersei, and the Hound has returned North with Jon to battle the army of the dead. With so much happening over the course of the final six episodes, it seems that there may simply not be time to bring the brothers back together one more time - even for the fight that fans so desperately want to see.
The moment for a one-on-one Cleganebowl seems to have been missed (although it's still a definite possibility in the books), but it's possible that the brothers will still have a final showdown - as part of their respective armies. A recent Game of Thrones season 8 magazine cover showed the two crossing swords, and while this may mean nothing, it could well be hinting at a battle. If it is, it stands to reason that the two would meet in the final battle between Jon/Daenerys' army and Cersei's. This might not have quite the same impact as a formal duel, but it could turn out to be even better. The Mountain has already had his epic duel scene, and seeing the brothers bump into each other mid-battle would still have all the emotional impact (and cool swordplay) of the original Cleganebowl theories.
Of course, all this is speculation, and there are other possibilities. Rather than a great battle, Cersei and Jon could agree to a battle by combat... with the Hound and the Mountain as champions (and what an end to the series that would be!). Other theories suggest that the Hound could be the one to kill Cersei, which would mean fighting his way past the Mountain first - or even distracting the Mountain with a fight while Arya (or another) steps up as the Valonqar. However their final fight happens - if it even does - it's time to recognize that the original Cleganebowl (the brothers formally dueling it out in front of an audience) should be put to rest... and hope that a bigger, better Cleganebowl is on the way.