It would be a great idea that to have it as a hammer instead, but in terms of greatest weapon ever, I don't think much else comes close to BG2 TOB weapons.
Just started TOB on my solo BG2 replay. swinging around the Carsomyr on a F/M/T, and backstabbing with staffs, OH look, a big evil lich, lol dispel, dispel, dispel with every hit, bye bye protections and interrupt every spell cast.
Also Grandmastery for multiclass hacks, 5 pips in 2H swords and Quarterstaffs. 10x Greater Whirlwing and Critical Strikes, then loading up on epic spike traps next.
I'm not looking forward to soloing the demogorgon on Legacy of Bhaal though, +200 HP and the only thing with timestop immunity.
This strikes me as some weird humble brag that has very little to do with the coolness, inventiveness, lore or flavor factor of a weapon itself. You only spent half a sentence on Carsomyr itself, none on its history, design or significance, and sully it under meta expressions of combat effectiveness that mostly apply to any weapon.
Perhaps most egregious is that you aren't even a Paladin and are apparently leveraging Use Any Item (UAI). About as silly as doing the same for the OP heavy block of stone as a little thief, though you MIGHT be able to conceive of an interesting reason why and how a thief would be doing that with UAI. You haven't mirrored the flavor of the amusingly stupid and stupidly strong Barbarian who ripped the thing.
I mean congratulations on breaking a party based role playing game down into a Diablo game or whatever, but that's a little off topic and OP has certainly presented a more compelling story.
So... what makes Carsomyr interesting and what am I supposed to imagine by a highly meta F/M/T wielding THE HOLY AVENGER, a holy blade restricted to non-evil aligned Paladins?
That's the kind of spontaneous storytelling I play DnD for.
Exactly!