I got past the Greenflower Eggman boss in ultimate mode.

[Beanb]

Now I feel godly.

 

[CloneFighter]

now beat THZ

 

[HPR]

you just gotta beat the game 200 times in ultimate mode to unlock shadow

 

[GrayAngel]

Ultimate Mode? What's that?

 

[Julia]

Ultimate Mode? What's that?

Check out the wiki.