Thunder: Used for stuffing approaches and forcing approaches. Combos into dash attack at short to mid range. Good against opponents who don’t know how Robin works and just run in. If you can’t afford to wait for Elthunder, throw this out.
Elthunder: Your bread and butter. If you don’t know what kind of charge you need, charge up to this because it’s useful in every match up. Offstage sniping is its obvious use, but it’s also an essential part of your melee game plan. Specifically, Robin often doesn’t have the speed to keep up with opponents who dash, drift, or roll away from her, but Elthunder almost always does. Opponent tries to back roll out of Arcfire? Elthunder. Opponent ate a dash attack/nair and missed their tech? Elthunder covers regular get-up, get-up attack and roll away. Opponent air dodges through your aerial and DI’s away from you? Elthunder to the face (or back). Elthunder is Charge Shot’s little sister and can be used in a similar fashion, or you can just throw it out there because why not.
It’s worth noting that Elthunder is the preferred charge level against opponent’s with reflectors, as Arcthunder and Thoron are often too slow and/or too commital.
Arcthunder: Used for prepping a shield for shield poke (such as with Arcfire), poking through a damaged shield, and setting up a follow-up grab. Best in situations where you are cornering/ledge trapping your opponent (consequently reducing the distance between you and minimizing their available maneuvering space) and for when YOU are being cornered/ledge trapped. Somewhat good defensively against rushdown characters as it forces them into shield and can buy you a few seconds while they wait for their shield to recover.
Thoron: Laggy and committal, but has incredible range and kill power. You can cheese people out with back throw + Thoron and forward throw + Thoron at low percents for free kills (not true combos, ofc, but will kill them if they’re sleeping). Can hit-confirm into it with Arcfire. Thoron beats out or passes through all other projectiles, which helps you secure kills against other zoners. Most importantly, it also outlasts air dodges; if your opponent has no double jump and they’re at medium % offstage, they’re dead and just don’t know it yet.
It’s safe only at mid-long range. If you’re fighting an equal or superior rushdown opponent and don’t think that you’ll have that kind of space, use Elthunder or Arcthunder instead. Holding Thoron effectively removes your other charge abilities until you fire it, which can be a death sentence in aggressive match ups. The only time that Thoron should be charged in these situations is when you’re fighting an extremely small rushdown opponent


who simply can’t be hit by the other three charges. If this is your only option, you’re in my prayers.
I hope this helps.