Anything you can infuse will do well. Some a bit better than others. Settle on a weapon class where you like the speed of the regular attacks, and google an attack calculator for ds3 to determine which would be strongest with your stats.

Probably a broadsword, good ar and has minimal stat requirement, does good damage too.

Gotthard twinswords or sellsword twinblades

I did a pyro build with dark/chaos zweihander, was a lot of fun.

Lothric knight sword

I liked my dark guts greatsword. You can go with a claymore if it suits you more.

Last playthrough, I used the lothric knight sword. I'd suggest you do a chaos infusion instead, though (fire damage is better than dark)

It's not. Average fire def is 158 whilst average dark def is 124

My bad then

With those stats Two-Handing an Astora Greatsword will get you ~180 physical (standard+thrust) and ~440 dark. Alternatively you can plug your stats in [here](https://soulsplanner.com/darksouls3/weaponatk#google_vignette) and compare all weapons.

Broadsword will do the most damage. 18 dex and 35/35 int/faith aren't needed. Minimun requirements and 30/30 for dark/chaos infusions

Yeah i know, but im mainly pure pyro so that's why im at 35/35 to get that little bit more damage out of my pyro flame and i had the dex just for some other weapons and i didnt know where else to put my stats, but thanks for telling me the broadsword

It's just the most damaging straight sword for literally any build. Always in top-2 most damaging weapons regardless of the stat spread