The Beast title in Blox Fruits is earned by defeating 25 Sea Beasts. One recent guide also notes that Rumbling Waters does not count , so you need 25 individual Sea Beasts, not the sea event version.

How to get it

  1. Hunt Sea Beasts until you’ve defeated 25 of them.
  2. Make sure the kills are actual Sea Beast defeats, not Rumbling Waters.
  3. After reaching the requirement, check your titles list in Second Sea or Third Sea to equip it.

Useful note

Some players report the title seeming bugged, but the common fix is still the same: keep defeating individual Sea Beasts until the counter is properly recognized.

Where to equip titles

You can equip titles by talking to the Titles Specialist in the Second Sea at the Cafe in Kingdom of Rose, or in the Third Sea at the Mansion on Floating Turtle.

TL;DR: defeat 25 individual Sea Beasts , not Rumbling Waters, then equip The Beast from the Titles Specialist menu.