Hey, I know you...
Anywho, a couple things I noticed that may or may not be helpful:
- obviously, each one of them has some sort of Achilles' heel and they will be immune to all others
- some of them have a Curse Mark-like passive where all their stats go up whenever they get hit. As such, if you're not careful with your team comp you could very easily buff them up high enough to OHKO all your guys.
- Characters with multi-elemental attacks are often useful, like Mu, Kinkaku, etc.
- some of them have mysteries that can cause immobile. I'm pretty sure most of the elemental ones have mysteries pertaining to their element though.
- Even if they're immune to a certain thing, debuffs like ignite and poison will still affect them. This makes debuffer characters like GNW Kankuro very useful. (At least, the ones I've seen in the exams will... idk if they changed it or not in the Ch. 9 ones as I haven't gotten that far yet)
If you're talking about the lightning ones specifically... characters with lightning-element standard attacks include Lightning Main (third one, and possibly second), Sasuke (both regular and playboy), and Kakashi. There's probably a few more that I'm missing here as this is off the top of my head.
Hope this is helpful at least in some way.