Super moves would be much like the Final Smash for Pikachu and Lucario in Super Smash Brothers Brawl. Completely overpowered attacks that demonstrates the awesome strength of said pokemon.
They all have to be based on some sort of move originally. Like, Lucario's Aura Sphere, would become Aura Storm according to SSBB. Be creative, and if you have a super move, naming it would give you brownie points for being awesome.
Now here is the rules part of it.
Just because it's your OC's Ultimate all out, super attack, last resort move. Doesn't mean that the opponent faints, or even hits. Especially if fighting another RP'er's OC. That being said, it is important to play into how powerful this attack is for the other person. No matter what pokemon it is, it will always hurt if it hits. Even if they dodge it, they should affected by the attack in some way. Either impressed, or shocked. If your OC does get taken out from a Super Move, that's just great!. Allowing your OCs to fail an encounter shows good sportsmanship, and great RP.
Second thing is that you can only use a Super Move once per RP. This includes follow-ups, though follow-ups have a special rule. Every time a day passes, they can use the move again. So basically, one Super Move per day.
Also note that this move will drain the pokemon of so much energy, that it makes every move after that much weaker. Let's say a Pikachu did a Super Thunderbolt. That pikachu's next Thunderbolt, or Volt Tackle wouldn't give the same shock as the ones before he used it. It would feel like said pikachu was ten levels lower than it actually is.
Combined Super Moves are devastating, and would most likely cause a lot of fear to any opponent. Super Moves can't be used by anyone. They need to discover their abilities themselves. Having an RP where they learn their Super Move is great. Super Moves aren't just attacks. They can be buffs and debuffs too.
Here is an example of a Super Buff. Haxorus uses Super Sword Dance. His attack skyrockets and he becomes amazingly strong with his attacks (nothing else though). But after three posts, he runs out of energy, and gets exhausted.
Here is an Example of a Super Debuff. Arbok decides it wants to use Super Glare as it is it's signature move. There is two things this can do. It can either be a amplified version of it's original effect. Like cutting the attack down to nearly nothing. Or it can be such a impressive glare, that it will affect more than one target. Since Glare is a single target only move, it would be suggested that it gets amplified, as it is the move's original effect. If you decide the move should be one that affects a ton of targets, it's the same as the original move, but affects more targets.
If you were to use a debuff move that normally affects multiple targets, it either hits three targets with a slightly lower debuff than on a single target, or have it hit every opponent on the field with the move's standard effect. (the debuff rules are very iffy as of now, so go ahead and make suggestions!).
Certain moves are unique and can't be pointed out here. Be creative!. I'm sure you are all fancy and able to get a good idea of how your move works!. If it doesn't work like anything that could be explained here!. Remember to always point out how your move works, no matter if it's special or not.
This was put here more to make a guideline when to go anime crazy in the RPs. I expect this to be used often ish, in RPs since they are fun. Who wouldn't want to do a thing where even though your OC was hit with something devastating, they could stand up, crippled, but strong, and do one last devastating attack before either being defeated, or winning bare bones. Just to make it a more attractive option to lose to such an attack. You get 200 Exp if you get knocked out in a battle where a Super Move was used against you, and on top of that, you get the normal Exp you'd get for losing the battle itself. To make it even more attractive, it doesn't stack with the Exp per RP limit~. But of course I have to make the rule that you can only get the bonus exp from being beaten in a fight with a Super Move once. (Note: Super Debuffs won't affect Super Offensive Moves' damage.
Remember to use this responsibly!. It would also be nice if you'd tell your RP companions that you are using it in the RP. If something is called "Super *insert something here*" it's a giveaway, but some like to be creative and call it "Mega *something" or a new move name entirely, like Aura Storm, which is a super version of Aura Sphere.
Anyway, have fun RP buddies :3