If you dislike slow two-swing swords try out something in the Brandish line (anything but Caurtery since it stops at 3*!)
The Levi is also awesome and doesn't have the slight damage determent to everything but Undead like the CIV.
Dread Venom is a sweet sword, but its usefulness is limited in T3 due to the low damage per swing and low knockback. Great for Jelly King due to the poison. I have one, but tend to only use it in T1/T2. I'll bring it to T3 if I want a challenge.
Almost no weapon in this game is outright BAD unless you absolutely aren't good at using it the way it's meant. Almost. There's a couple exceptions, and generally you'll probably want to avoid weapons that don't have later tier upgrades (The Cautery Sword, as culture mentioned, is only 3* and has no upgrades... and even for a 3* it is possibly the most underwhelming weapon I've ever tried)
I'm not saying "learn to play" so much as "keep giving different weapons a chance until you find one that works for you". With that said, the fireburst line is great for causing a lot of damage to a group, because it does STRONG fire quite reliably, while the iceburst line is excellent for crowd control. You can freeze half the enemies in a group and then beat mercilessly on whatever is left unfrozen, wait for the frozen ones to take a good hundred or so damage from unfreezing, and then finish off what little health they have left after that point.
The flourish line (and by extension the new Snarble Barbs) Are also nice and speedy and if you like dashing across the room while you skewer things, you should really enjoy them. Between any of the two, the only difference is that the Snarble Barbs have a spread-projectile charge attack while the charge attack of all of the flourishes is just a better-damage, reverse order of their regular attack combo. Between the various lines of Flourish, I can't imagine it being THAT big a deal since it's a choice between slightly more damage or a rare chance of a very weak status effect.
the Cold iron vanquisher line isnt borked.
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"The stat bars are wrong. The Vanquisher deals significantly less damage to all enemies, and only deals -slightly- more damage on Undead than the Leviathan. On top of this, the Vanquisher's charged attack has much less knockback, leaving you wide open to counterattack." -Gigafreak
While you are correct that the CIV does less damage than the Levi, I would disagree that it does significantly less. I and a friend did an experiment with a CIV and a Levi. Both Lvl 10, No UV's on either swords or on our gear. The gear we were using had no bonuses to damage of any kind. We found that while the CIV hit for consistently less damage, it was still rather close.
example:
Tier 2 Lumber Constructs:
CIV: 84 damage with 1 normal swing
Levi: 94 damage with 1 normal swing
According to the results, the Levi does greater damage. however, this greater damage is only of higher value by 10.
That is factual evidence.
This is my opinion: This difference in damage isnt as significant as it has been made out to be because with only a difference of 10 (in this case only) it takes the same number of hits to kill the Lumber construct. The amount of damage is irrelevant if it takes the same time and # of swings to kill.
The damage vs. Undead for CIV v.s. Levi has a greater difference than 10 in favor of the CIV which makes the CIV more efficient than the Levi.
Based on what I have found I would go with the CIV unless you never ever EVER plan to fight anything undead. Aren't there plenty of undead in FSC?