While the Rock and Cena are obviously ridiculously strong, don't sleep on Seth.
Cards have two purposes in this game, they give a special skill or quality to a character and will boost the CP level, giving them an overall buff. Equipping a full set will give an additional boost!
The most famous set is “My favourite thing”, illustrated by Kula, indulging in sweets. The set is extremely strong because it gives the player 5% boost per card and then 17.8% boost when the player lands a critical hit, thus 32.8% boost for 5 seconds, every time you get a critical hit.
The FES cards are of course better, but players will need luck to acquire them. The Noah cards, for example, give a huge CP boost and then 15% attack boost and super armour... if you missed a festival, don’t worry, there will be another stronger set in the future, that’s how the game works. For set cards, most players will use the Kula “My favourite thing” at 568 because of the skill but the highest CP cards are Kyo’s “The Start” set at 571/571/572, with the Art of Fighting “Sibling training” set with 570 each.
For option cards, from the normal pool, the cards average CP is 550, the highest CP is 569 which can be found with Kula and K’s Unreal peace and King’s Hospitality card. When equipping them to strikers, it is the same!
After that, the game released FES cards such as the Tekken set, False Halloween set and Noah set which had a CP of around 1K…. Speaking of Kula and her favourite thing, she had a robot companion, called Candy, which didn’t have a happy ending in The King of Fighters 2000... but is certainly cherished.
This set features Kyo Kusanagi in his outfits from KOF94-98, KOF99 and KOF2003. It's an interesting set because it first has huge CP and then it gives you a 4% power gauge increase from basic attacks. This means combo heavy characters, such as Ling, will get access to their supers much quicker, making them extremely dangerous. If Ling hits you with your back to the corner you might as well put the controller down. As soon as you even try to roll out, she can hit you with a super. There's no escape.
Aka The Mr Big set can be won from beating Inferno Goenitz. It raises your defense by 21% and gives you an attack boost based on 42% of your defence. This is exceptional for defense characters, such as Ash and Shermie, turning them into veritable tanks.
This set is notable because it is exclusively used for PvP. Collect shards from Inferno Goenitz to get this set (don't forget to use the reward summon tickets first). When an opponent attacks you after activating their super or hyper armour, the damage is reduced by 50%. This is extremely useful against Zero, Goenitz and Baseball Vanessa, when they catch you with their attacks. However, the best thing would be to avoid getting hit at all…
Light and Shadow
Aka the Noah set, showing all three faces of that ... character through the story. It gives the equipping character a 31% attack boost and a random chance to get super armour (10 second cool down). With the 3k CP boost, it's clear to see why this set stands above the rest.