Puddydog

For this fight like in many boss fights, only having high level cards isn't always the best plan of action. You want to have some level 0 cards because they can break any of his combos without you having to stock cards and then loss them, and you also want to have some other low level cards to do other sleights like ars arcarnum (excuse my spelling) and ragnarok (again my spelling). Both of these sleights are very powerful against single opponents but they are low level, arcarnum maxes at 6 and ragnarok at 9, so you will have to add in some different cards to your deck. To counter act the low level of those combos, before them I usually had a stun impact or strike raid because they stun your opponent and stop them from attacking you. Some other good sleights to use in any one on one battle are omnislash and sonic blade. Sonic blades back to back and can do a lot of damage.
Also, when I beat him I had about 4 cures. Whenever you run low use a curaga to heal yourself a lot of health. In addition to that you want to have at least 2-3 elixers or megalixers to bring back all of your cards like premiums and the ones that were first in your sleights. Having these be high levels is a good thing to have. If you always have them being broken put them in a combo so that their value goes up. If you use both elixers and megalixers use the elixers first because the megalixers restore the reload counter to 1 and if you run up the counter it may take time to reload that you can't afford. I recommend having Vexen as a back up to ensure that if he does get to you that you will be revived and you can heal yourself with a curaga. For this fight you CAN NOT use any card that has any relation to fire magic as that will heal him and partially set you back. By doing all of this I found that almost all one on one bosses were some of the easiest in the game.