I'll get this out of the way in the beginning minato will lose to current naruto current tobi madara and hashirama.(And probs sasuke once we see ems)
Besides the above mentioned minato should win every battle. People severely underate the power of ftg. I'm not trying to be like Kakashi fans and be like kamui gg. Honestly though how would someone combat ftg. For example somone like nagato would have severe problems with minato because he can just flee until he locates where nagato is hiding. Minato is probably one of tr best strategist so that is one reason why he would have upper hand against ninjas like killer bee.
The one ninja who can probably give him a good fight is itching because of his combo of smarts/skill. IMO minato can prob fight like a little girl and in until itachi becomes worn out. Itachis best shot is most likely genjutsu but besides that I think minato wins.
If you have somone that you believe would undoubtedly win please post who