Currently, its pretty hard to make a "true" sacrifice attack, where the character uses their last of their power and puts themselves in danger to try to wipe out the enemy. Sure, you can just set an attack to have like 10 self-damage when activated, but the problem is that when a character knocks themselves out, they always suffer a minor injury, which could either make those sort of attacks easily abusable (Since it isnt a high price to pay) or in need of nerfing, but that would take away from the "Desperation final attack" idea behind it in the first place
Of course, if those characters caused instant death, i doubt anyone would even use it, death is pretty rare in the game and does make the character unusable for a long time
My idea is that if the self-damage passes a certain threshold (Like "higher than 3" or "higher than 4", dunno about the balance there), the character who used the sacrifice attack should have to take a consequence roll as normal, maybe a "standard default" one, or as if they had been knocked out by themselves
In an ideal world, the consequence table would be harsher the more self-damage the attack costs (Like, if its 12 self-damage or something, there should be a considerable risk of death), but that may be asking too much