Hello Ciruno Fortes, it’s been a long time since our last debate hasn’t it? ^_^
Also, no, Garou would not be getting any Blacklight Virus powers - Garou’s Power Mimicry has only ever been shown to copy martial arts and physical statistics, along with allowing him to understand and manipulate the flow of energy (in which Alex Mercer’s abilities doesn’t involve any type of energy at all); he has never been shown to copy supernatural abilities outside of martial arts such as Esper powers for example, and he especially hasn’t shown to copy physiology-based abilities from others either (we don’t see him generate electricity bodily via mimicking an electric eel’s physiology for example) and Alex Mercer’s entire skill sets is derived from the Blacklight Viruses comprising his body and him embodying those viruses (with those viruses being the sole reason he has superhuman powers and abilities in the first place) - so as long as Garou lacks feats of mimicking physiology-based abilities, he would be unable to mimic Alex Mercer’s abilities via lack of feats alone.
Plus, Garou’s one feat of adaptation with Reactive Evolution to gain resistance was against Gyoro Gyoro’s psychic abilities and… That’s about it. Aside from that one instance, just about all other instances of Garou’s Reactive Evolution was all about gaining greater physical parameters, getting better at using martial arts, and basically anything else that isn’t gaining resistance to abilities. After all, despite gaining the power boost from God, Garou hasn’t shown that he can adapt to Blast’s ability of Space-Time Manipulation for example.
Either way, Garou’s one feat of adapting to abilities was against Psychic Powers (which are inherently energy-based in origin), he doesn’t have enough feats of adapting resistances to suggest that he can deal with superhuman biological contaminants that can rewrite his entire molecules from what I can see (especially since there isn’t enough feats to showcase how Garou’s Reactive Evolution would fare against abilities of non-energy based origin in terms of developing resistances).
However, I do agree that Garou’s Prior knowledge makes this too unfair against Alex Mercer. While Alex Mercer may have been granted access to Force Multipliers in this matchup for some reason, allowing him to fly out of the way of some of the attacks, Garou can create portals to attempt to BFR Alex Mercer to great distances away… Especially with the prior knowledge granting Garou information about Alex Mercer being basically too dangerous to risk fighting at close-range and would have to resort to use portals to BFR him away.
So, as long Garou has prior knowledge, this would become a mismatch - I would’ve argued that Garou would’ve been too boastful to use his winning condition moves against Alex Mercer at the beginning if Garou has no prior knowledge for this matchup… But he does in this matchup, so there’s basically little to no room of this matchup becoming anything more than a stomp now that Garou doesn’t have ignorance holding him back and basically resorting to BFR straight away because of it.