Zack doesn't ever use the sharp edge of his sword, he always hits with the blunt side. Therefore, he is doing more damage with a lesser attack.
Zack got killed by a couple of shinra guys.
Sure CC made him look like an all action hero, killing all those shinra army grunts, but tbh Cloud could have done the same, they were weak grunts with tiny HP, hell even level 7 Cloud could 1 hit these guys >.>
Zacks death in the original was a lot more stark and they only made him out to be some great American Hero just to milk the game.
Even in crisis core, that scene is almost the same. After fighting off thousands of soldiers and dodging missles, he is killed by the last two soldiers.
And to be fair, any character from ff would die if they were shot up all day.
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