We know sengoku the previous fleet admiral was a conqueror so it would make sense for sakazuki the current one to have it as well. If he fights luffy its even more inevitable
- Kuzan who fought sakazuki over the fleet admiral position is also an extremely likely candidate
- If both of them have it borsalino should
- Issho and aramaki but with them being admirals and their extreme beliefs of spreading their justice i think they should
- Garp while not technically an admiral is obviously a conqueror
