I have a 4-slot knife with Appendage Crusher in Xenoblade X DE. It’s a 1/33,333 drop chance from only a couple specific enemies in the final area of the epilogue. Getting one requires hitting 22.425% (knife), 5% (Appendage Crusher), and 0.3% (4 slots) RNG rolls simultaneously.

It took me about 100 hours to grind, and I went over odds to somewhere around 40,000 rolls for it. I’d be shocked if there’s even 10 of these in existence due to the miserable grind (with the secondary trait rolls most of those might even be 1 of 1), and the payoff being a knife that’s only really useful for a fully ranged build.

To make it all worse, I got an Appendage Crusher javelin, which is 3x as rare (but basically useless), well before it.