*spoiler*
He's the legendary super saiyan. And Vegeta pretty much screams about that the whole movie, and is cowering in fear from him, until brolli basically whoops the stuffing out of him. Very fun to see vegeta as a snivelin coward for once
When planet vegeta was destroyed brolli managed to save himself and his father using his incredible powers. Eventually his father found that brolly was insane (thanks to goku's crying) and could only be controlled by some special device. Eventually, after meeting goku for the first time in many many years, he snaps, the device breaks, he kills his father, and etc etc the rest of the movie. It ends w/ everyone lending their power to goku and goku punching brolli in the stomach reeaaal hard. Then its over and this planet which was created by brolli n his father is destroyed.
Then he comes back really strong in the next movie. It takes gohan, goten, and (much speculated) the "spirit" of goku, (cuz he's dead or something... supposed to take place after cell saga but before buu i guess) they hit him with a gigantic combined kamehameha and send him into the sun where he's fried for good.
There is no android brolli. Scientists merely salvaged his DNA and created a genetic clone of him. THis movie is just trunks, goten, and android 18. they fight him, although it isn't normal brolli... he gets some messed up toxic sludge stuff on him, and he basically turns into a big humanoid blob of guck that keeps getting bigger and bigger (this form is called bio brolli) and in the end he's killed by sea water, drying the sludge.:S