When you hit the axolotl with a sword, they show they're regenerating, to recover their health. But when you hit them again with a sword, they die. This is different on Java Edition, where after they actually regenerating, they still alive after one hit from the sword.

Step to Reproduce
1. Spawn an axolotl inside a 2x2x2 pool
2. Hit them with a netherite sword.
3. Wait until they fully regenerate (or at least, it shows they're)
4. Hit them again.
5. Repeat on Java Edition.
---> They die on Bedrock Edition, but on Java, they still alive.