As I continue my discussion of the various game system elements in Megaman Starforce 2, I think it is time to discuss the "Best Combo" system.
One of the most significant side-effects of the change from the Megaman Battle Network "Battle Chip" system to the Megaman Starforce "Battle Card" system is that it removed the structure that made the special chip combinations called "Program Advances" possible. With a Program Advance, it was possible to do things like combine three Cannon chips into a much more powerful GigaCannon attack, but this is only possible by combining the letter codes in certain specific orders, and as such the system is simply incompatible with the Battle Card system that does not use letter codes. Program Advances that relied on using battle chips of different types at the same time would be even harder to create and use in the Battle Card system. As such, Program Advances needed to be replaced, and the resulting system is the new Best Combo system.
The basic idea of the Best Combo is that, if you achieve certain conditions within certain battles, the player can record a chain of battle cards he used in battle as a "Best Combo", which allows that sequence of attacks to be used again as an unstoppable super-attack at a later time. Unlike the pre-built Program Advances, Best Combo attacks are designed by the person playing the game, giving them a lot of variety (though at the cost of making them less flashy and distinct). Of particular note is the fact that this system is thoroughly connected with the BrotherBand system, and encourages sharing Best Combo attacks with other players, so your own chosen "Personal Best Combo" becomes a way of showing off your own battle style and accomplishments to other players in a very useful and fun way. I love the basic concept of this system, but it does have a few flaws that still need to be sorted out.
One problem is that acquiring new Best Combo attacks can be extremely tricky. In Megaman Starforce 2, the rules for acquiring them are a bit unclear (as always, better documentation would have helped), and the changes in these rules from Starforce 1 have made it harder to deliberately set up an intricate combo, since an enemy attack will break the attack chain you are trying to put together. Also, the fact that you can only create a Best Combo against an EX or SP boss means that you can't create them early in the game. Fortunatley, these problems are minor, and it is easy enough to create decent Best Combos simply as a byproduct of fighting a boss well, so I will not complain too much about this.
A much bigger problem is that, in Megaman Starforce 2, there is almost no real practical way to make use of Best Combo attacks. In Megaman Starforce 1, it was possible to use a friend's Best Combo through the "On Air" system, but since the On Air system was removed from Starforce 2, you can only use Best Combo attacks through Legend Cards, cards that can be bothersome or expensive to acquire and disappear after a single use. As a result, it is simply impossible to make regular use of Best Combo attacks in this game, since valuable Legend Cards are only really worth using in SP boss battles and the occasional difficult plot battle. I don't think this is the best situation, so something should change. Simple solutions would be to either link Best Combos to Brother Cards again as they were with the On Air system, or to remove the unusual "can only use once" limit from Legend Cards. Since a freely-useable Legend Card would be about equal to a Giga Class card (which like Legend Cards is also limited to a single card per folder), I think it would work well enough with the latter solution. Certainly, the current situation, which limits the Best Combo system so much that it is nearly useless, is far from ideal.