Gogeta is a fusion between two verey powerfull Saiyan Warriors, Goku and Vegeta. His fusion dance counterpart is Vegito. Gogeta is non-canon meaning he never appeared in the manga. Gogeta's attitude is very serious and finishes off his opponent quickly, however when he becomes Super Saiyan 4 he is cocky and overconfident much like his Potara counterpart. Gogeta is many times called the strongest warrior in all of Dragonball as well as all of fiction.
Gogeta is very powerful and a great fighter, due to him being a fusion between the two strongest warriors in the universe. When he first made an appearance he was easily able to defeat Janemba using a move called the Stardust Breaker which basically is a rainbow colored ball that is broken down into small particles of light and obliterates an opponent into glitter.