Killer must have some special power/moves which Oda hasn't shown us yet. Going simply with what we saw in manga before, he's a fearsome combatant and very agile. The fact that Killer being a Supernova even if he does not look like one, makes me curious about his power.
I also feel that Hawkins has a high potential. On the other hand, I have no faith in Capone Bege.
I have faith in all of them, but I hope not all make it in the New World.
Oda needs to let one or two of them fail in order to not undermine the famous "cruelty" of the New World. The second part of the grand line is supposed to be a nightmare where only the absolute strongest survive.
I don't want to start any powerlevel discussion, but lets say Oda agree's and needs to sacrifice a Supernova in order to show that the NW lives up to its reputation. Which crew would he choose?
- Straw Hat pirates - No question. The complete failures are over. Set backs, maybe, but nothing major will happen again.
- Kid pirates - No question. Alive and kicking, challenging the Yonkou. Unofficial rivalry status with the SH's.
- Heart pirates - No question. Shichibukai status, they can basically do what they want. Law is hax too .
These 3 will make it, it is basically "confirmed".
- Bonney pirates - I think everyone agrees that her role isn't over yet. Being caught by BB doesn't really count as a NW failure as well.
- Hawkins pirates - The way Brownbeard talks about him suggests that he is alive, means he made it or is under a Yonkou.
- Drake pirates - Possible that Kaido crushed him and his crew. But why the buildup concerning his life as a marine, the references to the pacifista project?
These 3 could still fail, but it is very unlikely in my opinion.
Now, this leaves us with:
- On air pirates
- Firetank pirates
- Fallen Monk pirates
One or two of these three need to fail. Not because they are weak, but someone just has to. What was the point of the SH's 2 years intensive training if every other Supernova could do just as good by simply jumping in? There needs to be an incident that shows that it was wise to take their time before approaching the New World, else the whole hype and buildup was for nothing. Apoo, Bedge and Urouge have interesting design and powers, but they don't have the luxury of special plot relevance (yet).