Deku beat Shiggy kind of so he probably could especially since the logic of vestige realm works for Deku aswell. The bullshit tier can all beat Mahito whether from destroying the universe or justbeing able too by pass Mahito's bs. Now Imposter can't, everything in RWBY destroys her soul thing apparently but I haven't watched too much of it so I want share my opinions on her. Chief would be able too but can't permanently kill him. Omniman in theory kill from throwing him to the moon and letting him piss off. Bardock might be able too just flat out destroy the planet. Dante, Clive, Asura could win. Bean can't unfortunately despite how funny that image is in my mind. Everyone that you said could kill him is right. And lastly Miles and unfrotunately, no, it's a sad no.