E.g.
"CustomPotionEffects:[{Id:21,Amplifier:254,Duration:200}]"
...decreases Max Health by 4 in Minecraft 1.10.2, but in Minecraft 1.11 it increases Max Health by 4.
Related issues
Comments


Both a duplicate and intended, you can no longer get negative potion amplifiers.
Dupe of MC-10755