A recent thread on Reddit gave an interesting theory that the next League of Legends champion expected to join the Rift, Yone, might have an ultimate ability that was originally planned for his brother Yasuo.
Out of all the League of Legends characters featured in the official lore, Yone is probably the most popular one that hasn't become a champion yet. A series of interesting leaks along with the teaser Riot have recently revealed proved that he will most certainly become the new League of Legends champion.
Just like it was the case with Lillia, Yone's official confirmation and ability reveal will most likely take place on the same day which is suspected to be July 22 or 24, at least according to the Spirit Blossom timeline in the game's client.
However, according to an interesting Reddit thread , we may already have some hints on what his ultimate will look like. Apparently, it was shown in one of the focal points of the teaser - the moment when the demon-like creature is sliced up by Yone, which seemed like a finishing move.
The thread pointed out an interesting fact that Yasuo was originally planned to have a similar mechanic for his ultimate before Riot made the decision that they wanted a dash ability to be a core part of his kit rather than one he could use every minute or two, which led to his Sweeping Blade (E) becoming what it is.
This could become true considering that Yone is Yasuo's older brother by whom he was originally killed. The comment session also gave some interesting theories, one of which states that his finisher could be a combination of Zed's and Akali's ultimate - a dash with delayed execution damage.
Also, according to the video, Yone had to go through a power-up process before landing the finishing blow which could be translated to his in-game mechanics. Similar to Shyvana or Gnar, Yone might have a bar that he has to charge up before being able to use a particular part of his kit.
These theories should be taken with a grain of salt since the only thing confirmed for the new champion is that he will be a masked mid lane assassin.