The Dark Side That Resides Within You...

This picture displays a depressed Mario with a shadowy and evil doppelgänger of Mario in the background. This picture is based on Super Mario Bros. X: Sea Side Adventure. So Mario also has to defeat the monster that resides within him. That's not Shadow Mario, but a dark Cosmic Clone who looks identically similar to that of Super Mario 3D Land's.

Mario, Cosmic Mario/Cosmic Clone and the Mario series © from
Super Mario Bros. X: Alternate Kingdom, Super Mario Bros. X: Sea Side Adventure, Super Mario Bros. X-2: Invasion of Sea Side and the Super Mario Bros. X series © from and Prince Ludwig.