Just as Youko Recca said,
Flame of Recca
Yu Yu Hakuho
s-CRY-ed
Naruto
are all good choices. Some others to check out might be Orphen (has some cool magic, pretty powerful stuff
) and urmm....Hunter x Hunter might be good. But if he was looking some with really super like powers, Yu Yu Hakusho is probably the way to go. Similar powers to DBZ, and it has a better plot. (What doesnt have a better plot than dbz?) Flame of Recca is also kind of high on the power scale...although in a slightly different way and Scyed is just big power + lots of action = coolness. (Although it was just a good series and not great it may be just what your bro wants)