>>36326247I've had three so far.
Stakataka - I tried catching it with a Luxury Ball, but even when paralyzed, at 1 health, and with Roto Catch, it kept breaking out. It killed itself. I reclaimed it about half an hour later when I decided to forego the Luxury Ball and just use the Beast Ball.
Celesteela - I soft reset over a shiny once. I was able to reclaim it about two days later.
Barbaracle - Stumbled upon a shiny in a Warp Ride. It OHKO'd the Absol I travel with, which was my only Pokemon on hand. I reclaimed it eventually, not because I really like Barbaracle, just out of annoyance.