NOTE: This is in Strength wise, if I were to count the intelligence wise, then the list might have been slightly altered namely Vexen and Zexions places
Well I beat KH2 3 times on the Japanese version (born and raised in Hiroshima for 14 years so I know Japanese =P), and I beat the American version on proud mode (I am still trying to finish every little aspect in the game I just finished Seph off)
I also beat COM 6 times on both Sora's and Rikku's, so with all this information I have, these are the organization members that I believe would be the strongest from 1 being the best to 13 being the worst
1. Xemnas (He has practically all the power of the organization when you fight, just not Roxas)
2. Roxas (Though many say he should be first since he is Sora's other half, know this...Sora did not fight Xemnas until Roxas was already defeated by Sora in that one duel, which meant that Roxas went back to Sora)
3. Marluxia (He was the final boss in COM, and was stronger then the rest of the other boss fights in COM which means that he was no push over to the other members)
4. Saix (In a way he was second in command, he knows how to crush a heart, and he was the second to last organization boss fight, which shows he was really powerful)
5. Xigbar (He has long range, and though he needs to reload, his bullets pack a mighty punch)
6. Xaldin (He can play with peoples emotions and control all those lances)
7. Axel (He wasn’t as strong as some might have hoped for, then again people mainly just like him for his looks wich is some what shallow, but he did manage to take out allot of nobodies at the cost of his life)
8. Lexaeus (He had great brute strength but that was mainly all he had)
9. Larxene (Yes I know even though she was bitchy, she still was some what stronger then some others, and has mighty speed)
10. Luxford (He was just a gambler that had some tricks up his sleeve and was really easy to beat)
11. Vexen (He was barely a challenge in Com and Axel was obviously stronger then him)
12. Demyx (This guy was a joke he was not hard at all in the game, I thought he would put up a fight but all he did was mainly summon crappy water clones that’s it)
13. Zexion (Well most want to believe he could have been the strongest but that fact is, even if he could fight he wouldn’t be all that strong because Xemnas would have had the same power as him like he had with every one else besides Roxas, at most Zexion would be around 7 or 8, he was mainly the brains and mastermind)