I don't think Metal Bat scales to Garou yet. For one, Garou even
says that he mustn't talk tough because he was beaten by his human form, which implies MB is still inferior to Garou. The second thing is, Metal Bat only tanked a blow from an antenna, which should be calced, but I doubt it is 6-C.
Also, on Darkshine and VFU. This hasn't been said yet, but Fuhrer Ugly gets stronger via humiliation, and the result of that feeling is getting bigger. The bigger he is, the stronger he is. But when he was VFU, the acid prevented him from growing even if he was humiliated, because he needed to regenerate constantly to not get melted and disappear. VFU is as big as Darkshine, but he was much bigger before getting eaten by Gums. So I'd say peak Fuhrer Ugly (the version that fought Bang) was probably way more powerful than Darkshine.