I have a question regarding this figure, its trait says:

Streets Like a Jungle: Stealth. When Black Panther KO's a character, he can use Charge as FREE this turn.

does this work as the prime vulture from earth x, where you can charge more than once if you ko a figure with him?

If it is not the case, why not?

thanks in advance.

No, this does not work. You can only do the same free action once per a turn. Vulture's power is "at no cost" instead of "free". You can do "at no cost" actions multiple times in the same turn if you meet the requirements to activate it.

A big difference is also that Vulture needs to do his Charges after resolutions, so you can't do anything in between. Black Panther here can activate his FREE Charge at any point of the turn (after the KO, of course), so you can do other stuff in between.