~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
Bessy Mauler is one of the best weapons in the game, making short work of virtually everything and struggling only against Glacial Rift enemies. The damage output is simply insane, and its downsides are easily compensated for, thanks to the Lucky Strike rings you can buy from the Kitsune Den.17 agility is from starting as a catfolk-Thief-SLumRat/Hunter starting background, and the 17 strength is from drinking Rye Beer from Garth's bar, though if you're in the Glacial Rift, it may be worth it to drink Honey Mead for the Cunning increase instead, as crits become vitally important for taking down enemies with huge HP pools, as do stuns from the likes of Dastardly Trick, Stunning Fist and/or Banishment. In the Glacial Rift, you can't always one-shot everything, and I expect future content to reflect that.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ POWERS + VARIOUS COMBAT STRATEGIES
If you're running around in the Foothills, use Stunning Fist instead of Crowd Control because being disarmed makes you utterly helpless otherwise. If you're unafraid of this then Crowd Control is best for aoe, though it's not strictly necessary even for imps and harpies. If you're fighting enemies ith multiple phases or a mountain of HP, such as Bynervia, Grettel (to a lesser extent), or the Avanai Rider, letting loose with DT turn 1 won't always be a viable strategy, as you'll likely miss having it later in the fight (unless your enemy happens to be an elf that isn't a guard captain). Instead you may want to consider alternating between Sure Shot and your other ability or even attacking normally, because your raw damage and crit chance is enough to make even a sneeze from your mini-ballista a devastating attack. Save your explosive DT for when your enemy has run out of legs to stand on.
The reason why I'm using Foxfire instead of Arcane Shot is twofold: First, it gives me yet another useful thing to do when disarmed. Second, it applies a 3-turn debuff, not a 2-turn debuff, to which you can abuse Twist the Knife with, assuming your companions haven't put another debuff on the enemy. HOWEVER, obtaining FF requires you to sell your soul to Keros to become a kitsune, so Arcane Shot should work fine enough if that's not your thing. Other AWs aren't typically much to write home about, but Fading Blow is nice if your fucking mini-ballista is drawing too much aggro and you want someone else to take a hit. Your healer will thank you for it.
It may also be worth it to run banishment instead of Assassinate to yeet enemies that can't be one-shot with anything else, this is particularly useful with the double-giant fight in the glacial rift. Unbreakable is also worth considering, as it will ALWAYS save you from the most difficult fights in the game by making you invincible for three full rounds!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ COMPANIONS
Etheryn is your new best girl, as she can increase your initiative and, depending on your choice of set, can either apply Staggered to the entire enemy team, which is great for TtK, or can be an amazing healer that can increase your attack and accuracy to further levels. Then you have Brint, who provides +10 attack power and is a powerhouse in his own right. Notably, he can apply bleed for, you guessed it, more TtK fun. Arona and Atugia are dedicated tanks that wrestle with your BM for aggro, and using fading blow more often can help them draw the hits. Always run a healer in general. Finally, Kiyoko. Use her Kitsune-Bi set, apply a random 3-turn debuff to the entire enemy party, and simply blow them up with Crowd Control or Dastardly Trick. Any combination of these party members will work wonders with your BM build, but the most reliable that I've found is Brint+QR!Etheryn, even in the Glacial Rift. Ryn's healing can keep up with the enemy's damage output, while Brint buffs the entire party with damage and can sometimes apply bleeding himself, as TtK isn't always necessary, though he can be swapped out for a tank if you want to feel safe, or Kitsune-Bi Kiyoko if you're feeling risky (Keep in mind that she has a crippling frost weakness, which isn't very pretty in the Glacial Rift!). If you don't have QR!Ryn yet, use either Cait for healing, or Kitsune-Bi Kiyoko for her aoe debuffs, relying on the trick described in the next paragraph to go first.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GEAR
Now, gear: use lots of light armor. Each piece of Light Armor increases your initiative by 5, according to the wiki (I'm skeptical of that number so take this with a grain of salt). A clever technique is to always equip a Ranger's Bow, the +5 initiative belt, and Leather Spaulders before combat, and then equip the Winter Cloak, Champion's Belt, and Bessy Mauler immediately after combat starts. As it turns out, swapping gear in the middle of combat doesn't eat up a turn, so with Etheryn in your party this effectively guarantees that you go first on turn 1, but it does require you to remember to change your gear frequently, and also requires 3 empty inventory slots dedicated to gear swapping. This isn't strictly necessary, but always going first on turn 1 is nice, particularly if you're not using Ryn for whatever reason.
About the crazy-dangerous Glacial Rift: EPECIALLY keep a healer on hand 100% of the time if you're going there, the enemies will will tear down your health, even with your high Ward, which is necessary to survive the Avanai Rider's onslaught. Royal Leathers gets a special mention. It boosts your ward to high enough levels to withstand the onslaught from the Avanai Rider for several more turns, but dont fool yourself into thinking you're invincible! There's a reason why I recommended QR!Ryn above all else, and the Glacial Rift is that reason!
Again, save your DT for when the Roc is down, then finish off the rider.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FIN
And that's pretty much all I have to say about the Bessy Mauler and various combat strategies. It's an insane weapon and one of the best in the game, if not the best. And based on what the devs have said about most weapons being intended as "Sidegrades" that merely change your playstyle rather than function as direct upgrades, we can basically expect this glorious weapon to not be outclassed in a very long time, if ever. Hope this was helpful to you, and enjoy the screenshots I posted :^)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SAMPLES OF ONE-SHOTS (SPOILER WARNINGS)