After seeing collaboration sheet, I thought I'd share this. I've been working on it since subetalodge's weapon search is a bit limited.

It's also not the most accurate as it uses average of min and Max dmg (rather than every possible attack value), but at least it can produce ballpark Atk/Def calculations for specific opponents. For now it's limited to view only, but that should still be enough to see if there's any interest in collaborating. Entering all the weapons is quite the task alone, so please let me know if I should open this up for editing.

Spreadsheet

From the data entry standpoint seems like you could do it a lot faster if you just had the API datafile. This seems like a lot of work for somewhat limited gains over. subetalodge though. Subetalodges filters take some getting used to but you can usually find what you need pretty quick.

Is there an API? I found a super old post from Keith about adding one. The post had a link to a broken site, but otherwise, nothing really productive.

I'm not trying to put down their filter system, and I agree, that I was able to eventually garner the results I sought, but I still think this is worthwhile.

There's roughly 250 weapons for tiers 2 and 3 each and double that for tier 1. Scaling weapons don't appear in tier filters above their initial appearance and their scaling stats are just listed in the notes section. There's no sort option, so one has to manually review 25+ weapons per filter. If one wants to view all items of a pet's tier and lower, that adds far more to be manually reviewed. (For example, between tiers 2 and 3, the affordable [100k or less] bomb options only have about 2 total icons difference which, for some, might not justify a new purchase.)

Subetalodge has access to the API somehow, could always ask one of them how to get ahold of the info, or see if they could run you off a spreadsheet or something from their database.

I did a lot of searching on the database on threads coming up through tier 6 to tier 12 in the last year or so, going backwards in tiers is rarely the answer to your problem, I think I did it once for a water blocker against one of the challengers. I'm not saying subetalodge can't be improved upon, but your setting down a path thats going to be a TON of work, for I think marginal benefit.