For the believer in Jesus death is the final victory since it's the gateway into eternal glory, but I would agree that premature death is an enemy because a premature death will cause you to abort the fulfillment of your high calling in Christ. For the unbeliever, any kind of death whether it's premature or a long lived life is certainly an enemy because it leads into an eternal abyss with no hope whatsoever and it also stops you from receiving the glorious gospel.