What do you think of special moves in fighting games that damage the player when they use them?
I’m not a fan of mechanics that push both players closer to losing simultaneously, negative feedback. Mechanics like this could also be called Collateral Damage or Mutually Assured Destruction. The idea is, you’re taking damage, but hopefully you deal more than you take, and even though you’re wrecking yourself, you will push the game closer to ending faster and be on top when it does end.
You can think of moves like this dealing effectively less damage, since they’re damaging you at the same time, so you’re not gaining as big a lead over your opponent by using them. So if I deal 4 points of damage to you, and 1 to myself, I only really dealt 3 points of damage to you, but moved the game 1 point closer to overall conclusion. This can tend to make games more swingy, because it functions a bit like negative feedback. It also makes characters with this trait effectively weaker than characters without it, unless their damage is compensated for the damage they deal to themselves.
In a game like Smash where the amount of damage you can take isn’t capped, and isn’t directly tied to losing, this can work out slightly better, because you can continue to use the self-destructive moves ad infinitum, just taking on additional damage, instead of outright killing yourself. I take this tactic with Snake a lot. He can pull out grenades and go suicide bomber with them, and you blow yourself up a lot, but hopefully you blow the enemy up more often. Also when coming down, you can pull out a grenade and if the opponent hits you, it will cause you to drop the grenade. If they hit the grenade too, then it will explode, damaging both of you, and overriding the knockback of their move, usually for a lower knockback, which can help you survive a lot of hits. In this way you can evade death at great personal cost, while dealing damage to the opponent as well. Since there isn’t a fixed percentage that you die at in smash, you can abuse this a fair amount, and use it to turn the tables on your opponent (though of course, you come out a lot worse in that trade than they do).
Overall though, I think adjusting payoffs in this way doesn’t contribute significantly to the depth of a game. It doesn’t strongly differentiate the game states in my opinion the same way changing the physical characteristics of moves does. I don’t think Pichu is significantly more interesting for damaging himself, I think it’s largely pointless. Even if it is a cool touch for characters like Tien in DBFZ (and it works mildly better in DBFZ, because killing a character is a much bigger benefit than just getting a health advantage, so it can be a tradeoff of orthogonal assets, rather than strictly victory points).