WWE 2K24

This is very simple, once you finish all the Wrestlemania Showcase matches a secret match appears at the end. It’s a 30 man Rumble with all the legends included in the Showcase. Pick any of the 30 legends and win the rumble. P.S you enter #1

As mentioned in the other guide, you get this by winning the "bonus match" Rumble at the end of the Showcase.

Because you enter at #1, some people have expressed that they found it rather difficult to win, so I would suggest dialing the difficulty down to easy and choosing the character you feel the most comfortable with, especially one with high stats like Roman or Cena.

Note, if you're also going for the achievement for completing all objectives, this is going to require you to get a lot of eliminations, so try and use finishers as much as possible, as these make for quick eliminations.