This works for PCSX2 QT version (Nightly).
PCSX2 says “Memory card is corrupted.” Fix: You likely renamed a file that isn’t a raw .ps2 memory card. Use myMC to properly import. tekken tag tournament pcsx2 save file link
If you want to skip the hunt for a save file altogether, or if you simply can't find one that works, using cheat codes is the best solution. The PCSX2 emulator supports codes through .pnach files, and Tekken Tag Tournament has well-documented cheat codes for unlocking everything. This works for PCSX2 QT version (Nightly)
This is the trickiest step, as the file you downloaded could be in several formats. If you want to skip the hunt for
If PCSX2 throws a corruption error, the download was likely incomplete. Delete the file from your virtual memory card and re-download it from the link repository. Characters are Still Locked
: This utility allows you to open your virtual memory card files (typically .ps2 files) and import external saves.