Devilmite Beam is the best. Seriously. Relatively quick, just requires a hit to kill even the worst villans, and possibly even the purest saiyans when in super saiyan form. Why Spike doesn't fight as a defender of earth always got me, though why they don't always have minor fighters swarming with support or nonpower dependant attacks (both convential such as solar flare, destructo-disk, Healing and missilanous restraining techniques) and unconventional (Telepathy, Magic Touch if able to use, chocolate beam, roll call, time freeze, Telekinesis, Power ball and evil containment field) especially using multiform.