Here i show how to speed kill basically every enemy in the game (on normal difficulty that is). Essentially, the strategy revolves around stacking fusion comboing in a chain attack.
i player control Morag so i can quickly switch to Electra (probably the only reason to ever use electra) to topple since her blade cooldown time is much shorter than Poppi a's. Morag's hidden affinity tree also increases chain attack starting ratio which is why i use her instead of zeke. Since Herald (and all ether cannons) have low crit rates, I use Fiora and critical symbol on Morag to get Herald to over 100% crit rate, which allows her level 1 special to do over 400k damage per hit. Since it hits 16 times, this means she deals over 8 million damage alone. Player controlling Fiora also means the battle will end quicker since Herald's special pauses for a few seconds if it overkills.
You actually don't really even need Herald (assuming all your blades are S+) for this strategy; I mostly use her just to show how powerful it is. Obviously you can deal more damage by stacking blades with an ether mod on Rex; i don't just to show how powerful it is regardless