Bowser

Bowser is Mario's enemy in the Super Mario Series. He ussually appears in Mario games as the last boss and has appeared in several games alongside Sonic.

Mario & Sonic at the Olympic Games
Bowser appears in the Mario and Sonic cross-over title. He is a power type character making him slow but strong, making him good at the Hammer Throw event. He competes for Team Mario.

Super Smash Bros. Brawl
Bowser and Sonic both are fighters in Super Smash Bros. Brawl. Bowser uses his fire breath and brute strength to battle and for his final smash can turn into Giga Bowser, a more powerful version of Bowser and is bigger and has a more menacing apperance.

In Super Mario Series
In the Super Mario series, Bowser is the king of the Koopas and is the main antagonaist. He first appeared in Super Mario Bros. He has kidnapped Princess Peach several timesonly to be defeated by Mario. He has a son called Bowser Jnr. who he teams up with in Super Mario Sunshine to kidnap Peach while she is on holiday.