Here is the scene where Tino and his friends fights Bowser as Giga Bowser in Destiny Hearts.
(Bowser is getting weak from his first defeat as, Carver/Ansem appeared out of nowhere)
Carver Descartes/Ansem: Do you need some help?
Tino Tonitini: Carver!
Human Rainbow Dash: Is that--
Carver Descartes/Ansem: Yes. A Keyblade. But unlike yours, this keyblade holds the power to unlock people's hearts. Allow me to demonstrate... Behold! (staps Bowser)
Carver Descartes/Ansem: Now, open your heart. Surrender it to the darkness! Become darkness itself! (then he disappears)
Bowser: Ohh! This is it! This power! (laughs) Darkness... The true darkness! (Then transforms himself into Giga Bowser)
Tino Tonitini: Whoa! Bowser grows huge!
Human Rainbow Dash: Looks like we're gonna do this the hard way!
(They begin fighting Giga Bowser)