You really shouldn't push it and have some reservations. Yeah she just seems to have KO'd Lil, a captain, while he was even elf-possessed. That doesn't take away though that Lil is somewhat of a scatterbrain (and his elf persona doesn't seem to be any better) and that his order is currently ranked last. There's also more to being a captain than just having powerful magic. Above all though, there seems to be quite a few conditions that have to be met for her to reach this state. If she was able to do this nilly-willy, well there were some situations in the past she definitely could have used it.
Lastly Lil's magic is a very bad match for Charmy's magic. He fights with whatever he paints, thus all his paintings are magic and can be easily devoured. Someone like Yami though favors close quarters combat in sync with is magic. So that's a completely different fighting style altogether.
Yes Charmy has a lot of potential, but don't blow it immediately out of proportion.
Honestly I dont quite agree with some points. Lil guild coming in last doesnt make his guild weak. For example, black bull was last year round, and came in second simply by trying. That is also due to the releasing of amazing potential black bull has had over the years. I feel he is last cause hes young, and like you said a scatterbrain.
We look at his power, and was on par with yuno strongest mode/attack and lil wasnt going all out. This was enhanced by elf magic and he was going serious. Which charmy (granted in her new form took out quite quick)
The condition for her to reach this state is actually weird. Im going to assume a near death state. Cause up to now we havent seen charmy in a near death state. The only time we have seen charmy get serious is when it was dealing with food and when the spacial magic dude was about to kill finral. Versus the beast magic dude even though they was about to die she didnt even get CLOSE to getting serious. That lets me know that she is a scatterbrain similar to lil to be honest. She doesnt take much things serious that makes it worst. I always deemed her top tier ever since they sensed her mana being powerful and sinister similar to the elves and it was just food sauce on her face. That panel showed us that she has incredible mana.
We see alot of captains who arent worth nothing. Example would be the mantis guy, Dorothy, and even the purple orca dude before he got caught. We havent seen them do much except the mantis guy and all he has done was love to fight/kill. But when I say captain level I dont mean in terms of leadership i mean in terms of power. But you are right when you said her magic was the worst for lils and that yami specializes in short combat. But still charmy specializes in mid range and lets just speak hypothetically if they both were at prime blood lust state. I feel as if charmy could eat his darkness, and break his sword. Idk. to me i just think it could go either way.