I was bored and wanted to see if someone made a mod to add the minecraft bedrock version of the wither into java. I turned up empty (at the time) so I decided to do it myself.I tried to recreate the bedrock wither as accurately as possible... while not actually playing minecraft bedrock myself.

Version Compatibility:
1.16.5 - should work as intended
1.17.1 - should work as intended
1.18.2 - should work as intended
1.19.4 - should work as intended
1.20.4 - surprisingly, still works

Comparison
Java:
Flies directly above player, or directly on the player in phase 2
300 health
regens health

Bedrock:
Flies around randomly and shoots the player from various angles
Shoots many obsidian breaking blue skulls
Explodes and summons wither skeletons when converting to phase 2
charges and breaks blocks in phase 2
300, 450, or 600 health depending on difficulty
Explodes on death
Does not regen health


Inconsistencies of my version that i don't feel like fixing:
1. Custom blue skulls not real blue skulls -
  blue skulls cannot be spawned with commands
2. skull attack speed does not increase -
  I felt that the side heads should be more involved with the attacks.
  The side heads have their own unique ai anyway and i didn't feel like fighting it
  I could change this one if people wanted me to.
3. death animation -
  functionally the same but because i can't do things with the wither once it dies, i just did something unique with the item instead
4. Does not attack the player that did the most damage -
  seemingly niche thing but i also have no way to deal with lists of dynamic values yet, ie. players and their damage
5. Spins when charging the charge attack instead of a nice animation -
  can't add animations and wouldn't be worth it to use armor stands


if there is any inconsistency that i haven't stated that i won't fix, comment about it and i may fix it... or explain why it may not be possible

Have fun with the datapack.