While the Rock and Cena are obviously ridiculously strong, don't sleep on Seth.
To boost your CP even further, get cards! Let's look at how to level up cards (in chapter 7 you can read about how to get more cards). As we know, cards in the King of Fighters All Stars can give your character special skills but they also give an overall combat point buff. Cards can be leveled up to their maximum quite simply with any cards at hand and then evolved.
The real challenge and real benefit comes from levelling up their skills. To do so we need to add cards that increase the probability of raising the skill level. Certain cards will raise the level by only a certain amount- what we want to do is to max out that probability. The best cards to do this are in fact cards that have been evolved. Before starting the process it is recommended to focus on skill levelling five star cards only. This guide will level lower grade cards only as materials. The first cards a player should focus on are the “Unreal Peace” or “Strategic Retreat” option cards and the “My favourite things” set.
This card only has level 1 skill. Even if you raise the card level to max, the skill level will remain the same with the attack boost remaining at 2.3%. If we manage to raise and max the skill level then this boost will go up to 5% which is an obvious benefit for the character that has it equipped.
The cards selected appear in the materials bar on the bottom left, under the card stats box. The cards pictured used to raise the “Favourite Thing” card are experience cards, they can only be used to raise the card level. They can never raise the skill level. The coloured material cards (purple, yellow and green) are skill enhancement cards, which are specifically made for raising skill levels. However, this can be done with action, set and option cards too.
In the material tabs the rarest and highest value for raising skills actually appear from top left to bottom right. As the cards rise in skill level, the value of each material card will diminish.
To note, even when you're leveling up just the overall card level you shouldn't max it out in one go because you may be lucky to get a bonus level up which could give up to double the experience.
To raise the skill level we need minimum three star material cards and as you add the cards to the material list you will see the percentage of the probability raise. Our aim is to get it as high as possible, up to 100%. If you wish you could gamble with a lower probability and save yourself material.
If you use a duplicate card it will raise at a probability of 100% you can use several cards in one turn and they will raise the skill level per every card used.
Ultimately the best cards are five star or 6 star cards and to level them up you will need a combination of four and three star cards that have been evolved with skill levels. After evolving, do not level up the material cards, it is their skill levels that counts for probability.
A maximum skill level means maximum benefits.
The roadmap :
Levels 1-6: use enhancement cards
Levels 6-7: use evolved 3 and 4 star cards
Levels 7-9: use evolved 4 star cards
Here is a video of a typical skill raising session.