First one I thought of was Powerslave, but then saw someone mention Ride the Lightning, which is a much better album - tho not as good as Puppets imo.
Ride the Lightning is such a massive leap forward from Kill 'em All, although there is some filler on side 2 and I'm not that much of a fan of Creeping Death either.
The album's only real let down is the fact that the producer somehow didn't pick up on how good a bass player Cliff was. He's doing stuff on Call of Ktulu that is just out of this world, but at times is barely audible.