While fusions had been an aspect of the Dragon Ball franchise in one form or another since early on, it wasn't until the Buu Saga that we got to see its potential. Fusions are essentially a way to merge two warriors into one body in order to form an entirely new being that not only had all the powers of the fighters but also had an additional boost that greatly compounded their already awesome power. This led to a character strong enough to beat pretty much any villain they came across.