At close range ya Regulus would never be able to react to Bowser although depending on the range Regulus could see Bowser running at him and do something because Bowser doesn't have anything on his profile that implies high travel speed. Also how long would it be realistically before Bowser decides portal is the out because he has so much magic that wouldn't work that Bowser just using magic until it works is more like spinning a roulette wheel until something works rather than a strategy especially since Bowser has no idea about the authority of greed.
again
SEVENTY
SIX
TRILLION
TIMES FASTER
Bowser might not have that much running speed (which is entirely negated by his Koopa Clown Car which travels faster than Regulus anyways), but he literally statues Regulus. Regulus literally cannot do anything to Bowser that Bowser can't dodge. Any projectile he uses would just get dodged, and any projectile Bowser actually does get hit by, Bowser is SO FREAKING FAST that he can literally just walk backwards and avoid the projectile before said projectile does too much damage
Yes, Regulus's dura negging projectiles do cleave through Bowser, but the instant Bowser feels the pain, he's just gonna jump backwards and prevent the projectile from actually going through his body and dealing major damage
on top of all of this, Bowser can just regenerate from all of this. Bowser doesn't have an OD, he just regenerates, and Regulus doesn't have any means of destroying all of Bowser's matter since the only reason why Regulus can beat Puck is cuz he can destroy his OD, which CAUSES Puck's regeneration. So Bowser regenerates from anything Regulus throws at him, and therefore Regulus can't do diddly squat
Side note: Now that I think about it is it in character of Regulus to brag about his authority and what it does after stuff just doesn't work on him, I wouldn't say that's a win con by the way I'm just saying it's funny to imagine Regulus screwing himself over by bragging to a turtle wizard.
this is also a good point, meaning Bowser, being an Extraordinary Genius (for some reason), wouldn't be dumb enough to fool around, even if he's fast enough to do so. If Regulus brags about his powers, Bowser's just gonna choose smthn that actually does work
To be fair that's combat and reaction speeds, I don't see anything on Bowser's profile that could imply he has the travel speed to literally outrun the attacks Regulus has even if his combat speed means he could side step them so long as Bowser learns what attacks he's dealing with (eventually) and so long as Regulus doesn't have Danamaku that makes dodging impossible.
Koopa Clown Car makes this a complete non factor, on top of the fact that Bowser is significantly faster than the characters of Re-Zero, who can all react to Regulus's attacks and tag him, not to mention Bowser scaling to Mario
heck, Bowser's travel speed is enough to
outrun black holes and
chase Starship Mario with his meteors so dodging Regulus's attacks shouldn't be any issue at all
Seeing Regulus's attacks is also not an issue due to Bowser's Extrasensory Perception and Clairovoyance
he does actually, he was able hit Reinhard who was both millions of times faster and can dodge literal undodgable attacks. His normal AoE is like trying to dodge rain in a rainstorm, with a flick of his finger he decimated 1/3rd of a city.
Bowser would just tank and regen from this, Regulus has no way of bypassing Mid-High
I don't think he would. His final battle against Emilia, Subaru, and Reinhard. Subaru has Reinhard try all sorts of stuff to get around Regulus's invulnerability. And Reggie is actually getting pissed about it. Regulus repeatedly tells them to give up and that nothing can hurt him. But he never reveals how it works. Subaru had to use his name to figure it out.
Saying it out loud I guess that means it's also impossible for Bowser to figure out since he lives in another world where the star constellations would be different.
oh ic