I think the idea of an OHKO super is an interesting one, but of course the risk exists that it might feel unfair. This is particularly important considering this game is being marketed towards people new to the FGC and if something feels too absurd, even if it can be countered well by good players, it could put them off the game.
I thought about it for a while, and I believe there are two conditions that are necessary for an OHKO move to feel fair:
- It should require some setup from the player using the move to make it hit.
- It should also require the victim to perform some action that is predicted by the user to make it hit (in particular, having an OHKO that hits if the user DOES NOT perform a certain action feels cheap).
One example I came up with was a character who places something on the ground, and his OHKO can only hit you if you get hit by the thing on the ground as he's doing it. I eventually ended up fleshing this out into a full character design. I have no idea if this fits with the design of this character at all, it probably doesn't, but I think it's illustrative of how an OHKO character could work.
A button attacks: Low A is a low kick that is fast but has little range. Stand A is a big sword slash that has a lot of range but isn't very fast. Back A is another sword slash that goes the other way, and is even slower but has some use as an anti air. Low A combos into Stand A, which is his best combo. Air A is similar to Stand A, which is great for air to air but not great for air to ground. All of them do 1 damage.
Grounded B slams the ground with the base of the sword and creates a little purple vortex on the ground. The move can hit, which knocks down and does 1 damage. It has a lot of recovery and is punishable on block. The vortex lingers for a while or until the user is hit, and if the opponent touches it, they get knocked back a bit, take 1 damage and suffer hitstun. It's possible to hit them afterwards with stand A (low A usually won't reach due to the knockback), but this needs to be done predicatively as the hitstun is short. Air B is the same idea but he falls downwards with it. This can be used as air to ground, but it still knocks down on hit and is punishable on block so it's not a great option.
Ground C is a counter. It counters any attack from the front, dealing 1 damage, and costs 1 health to use, regardless of whether it is successful or not. If it counters a grounded attack, it knocks the opponent down and away. If it counters an air attack, it knocks the opponent upwards and you can combo super afterwards for 3 damage. It does not counter crossups and has recovery, so if you guess wrong you eat a full combo.
I actually have no ideas for Air C. We'll just skip over that for now.
Air Super is similar to ground B, but it throws the purple vortex forward about 75% of the screen. It can hit, which does 1 damage and doesn't place the vortex. It also doesn't place the vortex if it gets blocked. Ideally, you want this not to hit so you can place the vortex behind the opponent.
Ground Super is very slow, charging sword slash that hits about half screen and does 2 damage if it connects. He can be hit out of it during the charge up portion and it is very punishable on block. The charge is very long, probably around 30 frames. The only ways to combo into this super are after a successful ground C after countering an air attack, or if the opponent touches the purple vortex ~25 frames after the charge starts.
Ground super is also the OHKO. After the opponent touches the purple vortex, they turn purple for the duration of the hitstun. If the super hits during this time, it has a special animation and it kills you, no matter how much health you have.
Obviously, this is super hard to set up. You have to input super about 25 frames before they touch the vortex, so if they just sit there, they can easily just block the super and punish. The main way to hit this would be to input super when the opponent is in the air in a situation where they'll land on the Vortex, for example, if they forward jump into it, you can press super during the early part of the jump and they die (though do note that if they can hit you in the air, the super gets interrupted and they don't die, so you either have to be far enough away or they must empty jump). There might also be situations where you could scare them into backdashing into it, but it wouldn't be as reliable. So how do you spook them into jumping onto the vortex? Well, that's the game.