My list of strongest to weakest Six Heroes currently is:
1. Terumi
2. Hakumen
3. Phantom
4. Jubei
5. Valkenhayn
6. Platinum
That being said, I don't think it's that simple. As I type I keep thinking that 2-4 are interchangeable. Hakumen and (I think) Terumi have referred to Jubei as the strongest creature alive. That being said, it was implied that he was ruffed-up by Phantom in the events that take place in CS. On the other hand he did go on to fight Relius, which I don't think is easy for anyone to do, especially when injured. There is also no evidence that Hakumen wouldn't get ruffed-up by Phantom also. However, even though de-powered, it's always Hakumen who gets called upon to do the hard work which buggers me a bit. Surely if Jubei is as strong as hyped up to be, Rachel would go calling on him to help take down Terumi instead of Hakumen. I mean, I do get that Hakumen is/was an unfortunately easy pawn to manipulate in his current state while still capable of fighting at a high-class, and I do get that Jubei may not want to get involved for whatever reason(s), but it doesn't even seem like the ask Jubei option comes/came to Rachel's mind... Ever... Maybe I'm just being a blind fanboy though. After all we haven't seen Jubei actually properly fight.
On a slightly different note, how did nine get the opportunity to cast Mind Eater on Terumi? Did she lull him into a false sense of security and quickly shout out "MIND EATER" before he could react (like word tag)?