I didn't put this in the Glitch section because it could very well just be me hallucinating or something :p
So I was just in the Battle Tree in my Sun game, and I was battling a trainer that had an Altaria. My Metagross was paralyzed, and it just kept using Roost every time I did any damage. I didn't want to deal with that, so when it was at what I'm CERTAIN was full HP, I switched my Primarina in to decimate it with Ice Beam.
So she uses Ice Beam… and knocks this Altaria down to red HP but doesn't quite KO. I'm like alright whatever, it can't do anything to Primarina, so I'll just kill it next turn. It uses Roost, gets to about half HP… Primarina uses Ice Beam, and… it doesn't die. It lives with a sliver of health. I repeat this next turn. Lives with a liver of red health. This goes on until I finally end up freezing it, THEN I manage to KO it.
I'm absolutely CERTAIN I didn't crit first turn. Primarina is really strong, Modest and has max Sp Atk. Altaria didn't have a Yache berry… there's no WAY Ice Beam was only doing half. I even just did a calc. Ice Beam still almost always OHKOs a Calm Altaria with max HP and Spdef and the best IVs possible. At worst, it does 90%. Wtf gives? Am I going crazy?