I guess that's why he needs to be kept sealedWell, it's not like it was ever said/confirmed or anything. It's just my interpretation from Igor's quotes. Here are some of them:
''Right now, you may be able to defeat that which cannot be defeated''. Meaning Minato can do the impossible.
''You have the power to bring about a new beginning, or the ultimate end''. Meaning Minato is basically in control of fate itself
''Nothing is outside the realm of possibility for you now'' Once again, meaning Minato can do literally anything.
Maybe he was speaking metaphoricallyThanks, I'm almost done Zzz
I can't resist chiming in here, so:
Personally, I'm not so certain about Minato's destructive power. Igor's quotes do in fact suggest a nigh-omnipotent level of destructive capability, but it's also possible that he's speaking metaphorically (as Minato learnt the true meaning of life and rose to a higher plane of existance).
But in terms of durability, the guy resisted death itself (not an embodiment or a watered-down version or anything like that, literally death) on sheer willpower, something that seemingly defies the laws of existance.
So, to sum it up, he's really, really, really powerful. The only other Persona character who has crazy feats like that is Tatsuya (though they're not as insane as Minato's).
That resisting death reminded me of Luffy