I can see the two duking it out for a time, with Thor using a mix of physical attacks and lightning strikes whilst holding a noticeable edge in CQC and Luigi trying to parry whatever Thor may throw at him and combining it with Zone Speed for easier dodge time
Luigi also wouldn't be as likely to use his Poltergust here, considering Thor is anything but a Ghost, however, I can see Luigi using it to benefit him in possible scenarios should the need arise
since Thor would probably view Luigi as someone of Earthly-roots, he'd be holding back against him, possibly giving Luigi enough time to cycle through his options and resort to power-ups, eventually coming across some of his invincibility ones to heavily damage, or even potentially one-shot, Thor
could be wrong tho, and that's why I'm not voting yet