Just because you can make a boss revolving around instant death attacks, DOESN’T MEAN YOU SHOULD. FUCK JRPGS THAT DO THAT. It’s fake difficulty. plain and simple.
Prime example: Barbatos in the Tales of Series. Use an item? Best hope you have an auto revive because that character is fucking dead to No Items Ever. Try to revive them with an item? Now the OTHER character is dead, good job. If you give a boss instant death you better have a damn good reason/an obvious trigger. Mind you, I’m somewhat willing to make exceptions for optional superbosses. They cheat anyways. Example: Elizabeth in Persona 3. you fuck up and she instakills you. GG
Long story short: don’t invalidate a player’s setup with instant death spam. It’s not fun.