Here's the 19th Boss for Mario & Sonic Worlds in Danger: Captain Basilisx and Mecha Sonic. After defeating Bowser Jr and Metal Sonic, Bowser and Eggman accelerate their plans even further by releasing their strongest secret weapons on Mario & Sonic. And to ensure that Luigi and Tails don't interfere, Basilisx petrifies Luigi and Tails. Mario and Sonic get extremely ticked off and engage the two strong warriors in an all-out brawl.
Phase 1 - Mario vs Basilisx: Vim and Vigor - Kingdom Hearts Birth by Sleep
Phase 2 - Sonic vs Mecha Sonic: Crisis City ~The Flame~ - Sonic the Hedgehog (2006)
Phase 3 - Mario vs Mecha Sonic: The Deep End - Kingdom Hearts HD 1.5 ReMIX
Phase 4 - Sonic vs Basilisx - Give No Mercy - Newgrounds Audio Portal
Hammer Bro Mario: M-Haynes-productions
Fire Sonic: Exorz
Mecha Sonic: shadefalcon