Look at this thread, and you'll understand that you're mistaking about what you think that happened in the fight between Minato and Raikage:
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And what i say here has been confirmed in todays episode. Look at Rul sig.
Also, you seems to forget that will only a kunai, he was able not only to destroy Bees limb, but also create a crater at that point. It has also destroyed Tobis body which was composed from Hashiramas cells(a powerful Zetsu body), and also created a great crater at that point just with rasengan, which shows that he has some sort of strenght(probably due to Hiraishin speed). When he hiraishined on Raikage, Bee was forced to interved at that moment, because he knew that A would be dead if it had continued any further.
You also forgot about other abilities like Summoning techniques. If he uses Food Cart Destroyer on A for example, he is almost done for.