LINK: https://mega.nz/file/H8cklTZD#XWsqn0P16IpN1wCQsia5XbQRaIR4pNJq3DhnFdei2xg

I made a post on reddit but got shadowbanned for posting a link to archive.org :/

Check out kuroneko4696 and Darth_Agnon's posts below if you're looking for DLC for MH3G, MH3U, MHStories1 (JP and EU versions).

Contributors (thank them):

• /u/GrenderG (reddit) for working on goshawk (github.com/GrenderG/goshawk)
• /u/kuroneko4696 (reddit) for providing save files for various JP games and sharing DLC palicos for XX (Comment: https://old.reddit.com/r/mh4u/comments/1ca3yhm/looking_for_japanese_mh4g_dlc/l90rh8o/)
• /u/Darth_Agnon (reddit) for providing save files for various EU games (Comment: https://old.reddit.com/r/CitraPiracy/comments/kmrmxd/anyone_have_monster_hunter_3_ultimate_dlc/l4d6na9/)
• /u/StrawberryBusiness63 (reddit) for sharing 4U extdata (Post: https://old.reddit.com/r/mh4u/comments/1c3jgoh/how_to_get_mh4u_dlc_quests_post_3ds_server_shut/)
• @tetreos (archive.org) for backing up 4U savedata and extdata (https://archive.org/details/3ds-monster-hunter-4-ultimate)
• GreedLycaon (gbatemp) for originally backing up the most complete XX save I've found (taken without their consent) (Post #45: https://gbatemp.net/threads/clean-mhgu-save-with-full-dlc-mhg-transfer-bonus.543438/page-3#post-9958827)

also thanks to everyone who wrote guides, tools, instructions, and backups! I have tried to credit them where I can.

Screw reddit.

Update v1f (final):

• I forgot to include the text for the original post on reddit. It contains a lot more info and is more explicit about the sources. The file is included as "mh dlc compilation.md".
• The DLC cats "ぽかぽか" & "ミケゴールド" in the MHXX save had their info translated into English. The complete save now has the original text.

As long as I'm not forgetting any event quests, all the saves should be 100% complete.

Notes:

• The MHXX save doesn't have the USJ Real item pack, and not all DLC cats are available for hire. Nothing can be done about the former (afaik), and you can import DLC cats using a save editor with the included files.
• In MH4G/MH4U, some pieces of gear require "Elder Bfly Beetles", which can only be obtained through "Hunters for Hire". Use a save editor to hack them in.

Update 2024/07/16:

I have checked every event quest against Ping's Dex and can confirm that these saves include all of them!

However, many DLC cats for MH4G (possibly even MH4U) are missing. Nothing can be done about this until goshawk (unless someone has a source).

Happy Hunting :)

Update 2024/09/18:

The DLC Cat situation for 4G is a bit complex. (I still have no idea about 4U)

After a bit of research, here's what I've found:

Here is a page that lists every DLC Cat distributed for MH4 & 4G.

Assuming that the atwiki page is complete, there are 2 things relevant for archival:

1. The DLC cats distributed for MH4 (the base game, not 4G) were never released for 4G, so no legitimate 4G extdata will have them.

However, at least some (maybe all) of them are included within the Goshawk server archive, so someone could theoretically decrypt them and hex edit them into a 4G save.

The decryption keys should be within Goshawk, but here's a more useable link.

2. For 4G (and maybe even base 4), there were some DLC cats distributed at limited times and limited events (like USJ). The files for these cats aren't in Goshawk, so they seem to be lost to time and recreating these cats exactly probably won't be possible.

The atwiki link above does list the unique skills that these cats would've had, so it should be possible to modify existing cats to use them using a hex editor (or a save editor).

The 4G extdata I've included in the OP has all the 4G DLC cats that were distributed regularly, and the files for those cats are within Goshawk.

The extdata also has some limited release cats like Nanako G, so it's actually slightly more complete than Goshawk.

I have no idea if the stats & skills for these cats are legitimate (cheating was quite rampant in 4G), but at least for the cats that are in Goshawk, it should be possible to confirm.
For the other cats, I could compare with the skills listed on the wiki, but the stats might still be illegitimate.

I have managed to decrypt the 4G cat files, but I'm not in the mood to export cats and and diff them atm, so that'll have to wait for a future update.

Happy nyanting :P