His first form (called Janempa in the FUNimation Dub) is chubby and very large. Janemba's intelligence also seems limited; the only word he knows how to say is his own name. His attacks involve things such as creating miniature versions of himself and of Goku, creating dimensional portals, and shooting ki blasts from the 4 holes on his belly. Even in this base form, he forced Goku to transform into his Super Saiyan 3 form. At this stage, Goku easily overpowers Janemba, smashing his head into his body. After being defeated, Janemba transforms.
Janemba's second form (In Dragon Ball Z: Budokai Tenkaichi 3, this form is known as "Super Janemba") is much more powerful than his first and is more built for fighting. Janemba reaches this stage when his head is caved into his torso from Goku's punch, he then proceeds to compress his mass into a smaller space resulting in this new form. This form is able to use a deconstruction/reconstruction teleportation known as the Bunkai Teleport, portals with which he can attack through, able to stretch his arm at lengths, turning objects into deadly weapons, project his opponents' own ki back at them through portals, and wield a powerful sword capable of shooting unblockable Ki out in strikes, but Vegeta destroyed this sword. In this more powerful form, Janemba overpowers Goku even when he is at Super Saiyan 3. Even after Vegeta shows up and helps Goku fight him, Janemba is still able to effortlessly overpower the both of them. However, once they successfully fuse to form Gogeta, Janemba is unable to phase them with even his most powerful punches. In a short time, Janemba is defeated effortlessly by Gogeta with the Soul Punisher, restoring the ogre to his original state.