Kabuto's regenerative abilities take time. You could notice that
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from Sasuke's kusanagi sword on the head of the snake before it actually regenerated,
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. Notice that
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, Kabuto was blocked and his movements was restricted, only on
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did he finally escape in time thanks by liquefying. So Kabuto is still solid. Only after some times, can he regenerate. But if he gets killed before the regeneration, bah he is dead. What's worse for him while fighting someone like Minato is that FTG is instant, so he won't even have time to react, let alone his regenerative abilities having time to take effect.
Because of this, if Minato kills him directly by attacking the vital points or cuting his head directly, he is dead. And Minato usually
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when
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.
Even himself
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he could die, only that because of the fact he is controlling edo tensei, they can't kill him. Wounding him would be useless because of his regenerative capacities, but killing him is definitely possibly contrary to what majority of people think. So i don't understand why you think only way to defeat him is with sealing techniques
Besides, i see that Minato's rasengan is underrated again. Base Kabuto already had regenerative abilities, yet he was incapable to regenerate the damage inflected by half backed Naruto's newbie rasengan. Reason? Because rasengan does internal damages. Minato's
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is stronger than
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in terms of size and power(just look at the difference in damage caused by the 2).
Anyway just leaving this