So, what's the consensus on the best weapon, speaking purely on how much damage it can put out before depleting a stamina bar?
This is a difficult question to answer. But speaking strictly PVE...
Damage per stamina bar? Probably Blades of Mercy. But it relies on you to combo those moves out, meaning lots of inputs, and it's not effective at all against multiple enemies. It also can't be buffed with elemental paper and has very short reach. Still, if you successfully unload a whole stamina bar against a boss, you'll do tons of damage.
When it comes to balancing damage and the actual cost of stamina, Ludwig's Holy Blade is going to two or three hit every common enemy in the game and stun them in the process. All of its attacks combo into each other in 2H mode and 1H mode is fast, with longer than average reach, and a high damage output. You don't have to worry about chaining multiple attacks together and can very easily take on multiple enemies at once. So you might take out more enemies with your swings than the BoM. LHB can also be buffed with paper and the phantasm shell to exploit enemy weaknesses.
The Saw Cleaver is a really popular weapon. It has short to middle range options, so you can still possibly hit multiple enemies, and gets a 20% damage boost against beasts. Its stamina consumption is extremely low, while damage output per swing is much lower than something like LHB, you can do more damage with your stamina bar.
But, again, this is a really hard question to answer. It has much more to do with what you prefer than what does more damage.
Do you want fewer hits to do more damage in short bursts? Ludwig's Holy Blade.
Do you want more hits to do more damage in longer bursts? Saw Cleaver or BoM.
But you have other options, like the Chikage, but it just comes at the expense of your health while taking advantage of its full power.
