Brian isn't Taylor. At all. In someways they may seem similar, but they really, really aren't and it gets especially obvious when you really look at things. Like, you look at the Undersiders and at first you think, 'okay, so Brian's the pragmatic, responsible one.Lisa's the smart, knowledgeable one, Alec's the blunt, easy-going one, and Rachel's the crazy one. Taylor is the other responsible one.' But as you look closer, you see where that breaks down, and the biggest way is this.
Taylor's not the responsible one. Taylor's the bat shit crazy one--Rachel's just maladjusted.
Jokes of escalation aside, we all know how Taylor gets, especially given a goal to focus on. She's somewhere between unstoppable and suicidal. I want to be a hero--let me throw myself against Lung the first night out. I want to be a hero--let me take up an absurdly dangerous plan to go undercover with no experience. An Endbringer attacks and I have no way to harm it in the slightest? Let me rush towards the oncoming tsunami. Coil has Dinah? I'll do whatever it takes to save her. The Slaughterhouse Nine? Behemoth? The end of the world? Scion? I'll do whatever it takes.
And she does. She gives up everything to do that, several times. Once she starts going, she never stops and even though her power is nowhere near weak, she regularly goes off to fight people she just outright can't hurt. High risk, high reward; high risk, low reward. It doesn't matter. She starts and keeps going until she crashes or everything that could kill her is gone--and usually reached the latter first.
Brian's kind of the obvious. I mean, I know a lot of people have pointed out he's kind of bland--hell, even Wildbow's said that he needed to do more with him on the rewrite. After his second trigger especially, he almost seemed to vanish, even before Taylor became a Ward and when he died, it was hard to even notice. I like Gruea lot, but there's are obvious and definite issues with him on that front.
And I think the biggest might be this. Brian's pretty easy-going. He's remarkably well-adjusted for a Parahuman and he's usually pretty content, too. He wanted custody of his sister and not much else. When he got that, he wanted to keep what he had, protect his friends, etc. And...that's it. That was all he really did or wanted to do and so he was fine just cooling his heals afterwards.
The thing is, Grue is super powerful. He can black out city blocks with a gesture and everyone inside? Is fucked. Post-second trigger, Grue could easily claim to be one of the most powerful capes in the world, at least potentially. I mean, after he sets up his shit, 99% of all capes are fucked--he doesn'tjust steal powers, after all, he plunges anyone within into sensory deprivation, weakens their powers, and then steals them. If you put him against the Brockton Bay Protectorateand Wards? I'm pretty sure he could rip them apart on his own. In his darkness, most of them are screwed outright and the few that aren't couldn't last long once he starts juggling his powers. And he gets worse the more people show up. Honestly, I thought the Echidna fight was his worst showing by far, because holy shit--how are you having any problems whatsoever here? You can pick and chose from just about anyone you want. Same with the Behemoth fight.
When Alexandria threatened the Undersiders, when she told Taylor how she would take them down, I blinked and wondered what the fuck she was talking about. When, afterwards, Defiant pressed her, mentioning the danger they'd be in, how many heroes would go after them...I was scratching my head. Because if you send a horde of heroes into Brockton Bay, they're fucked. Tattletale means your odds of taking them by surprise are negligable at best and Taylor makes that even worse with her bugs. Imp is an assassin they can't notice or stop. And, once the element of surprise is gone, Grue crushes you. He blacks out city blocks, swathes massive chunks of the city in darkness that the heroes can't see in, can't hear in, can barely feel stuff in--and it cuts down their powers, weakens them even as Brian grows in strength himself. If Alexandria goes after the Undersiders, Grue takes her powers. Or Legends. Or whoever Lisa says is best for the situation.
And once you're down, once you're beaten, Regent takes you.
And then you add in Parian. Foil. Accord and his dudes. More options in their own right and Grue can take their powers at will. And you want to send a horde of heroes in there after them? What are you going to do, put them in the Birdcage? Are you out of your goddamn mind--you want a power copier in that place?
After his second trigger, even after Taylor, Grue and the Undersiders could do whatever the hell they wanted. Noteasily, perhaps, but they could. They could have expanded into Boston and New York easily. The greater the opposition, the stronger they are.
But the thing about Brian is, he's not that kind of guy. He doesn't care. You leave him be, you ignore him, he's fine, he stays put. He did for years, before and after Taylor. Even when his power was just at will sensory deprivation, he could have joined any major gang and gone far, but he's not really into pushing the limits or taking risks. What he wanted was to provide for Aisha, keep her safe, and that was it. Even after things went to hell, after Bonesaw, he didn't really care about much--not even revenge, really. He could have gotten it; pick the right capes to copy, find the Nine, plot things out, kill them; he could probably have managed.
Instead, he stayed put. Grew his power base, but safely, quietly. One of the strongest capes in the world, honestly pretty content.
Put in this situation, would he have done the same thing as Taylor? Almost certainly not. For one thing, if this was Brian without his trigger event, he'd be different but probably still well off-ish. He wants to help Aisha, but he didn't need his power to beat the shit out of his mom's boyfriend and getting her out of her drug addict mom's place was easy. There were issues between her and his dad, things he wanted resolved, but still, he was pretty good. But not triggering, not getting powers? That fucks Taylor up. She was near a breaking point even with them; three months without them and shit going awry? Damn. Is it any surprise this happened, that she mutated horribly?
But let's say he does, that he gets the same powers--how does he handle this. He reaches out to Contessa, gets her powers, and then what?
Honestly, he probably just leaves. See, Taylor could have done that at any time. The moment she got Doormaker's powers, she could have fucked off out of here. Brian probably would, maybe grabbing Doormaker and bringing him along so they couldn't easily follow. If Aisha was taken too, he gets her, reaches out to Panacea if she needs healing, and goes from there. Make it hard to follow, path to making it not worth hunting him down, and done. He wouldn't care about saving everyone Cauldron ever touched, righting every wrong, or any of that, just getting out and saving Aisha. Might also plot a path to fix things with her and her custody issues on that front.
Or, perhaps more likely, Contessa mindwhammies him. It'd be pretty easy. The moment he survives, proves he's alive, and shows his power...suddenly he's useful as all hell. A force multiplier. And Contessa could plot a course to getting him everything he wants and then some. Cauldron could german suplex Aisha's custody issue like it was nothing, get him money, get him set up, everything he wants, and make him a major player in the process. She could align her path with his and they could both get what they want; Grue would be a name mentioned alongside Eidolon or another of Cauldron's boogiemen. It would have been a win for Cauldron, even if Grue didn't like them; he's pragmatic and they have resources, access to other powerful capes.
He sure as hell wouldn't do what Taylor did, because he's not crazy. Contessa could have taken a lot of the fight out of him by name dropping Eidolon, someone he couldn't beat, couldn't model, but she didn't even try that with Taylor. Why? Because Taylor wouldn't have backed off, she'd just have gotten worse. She gets her powers, gets her PtV, and the first thing she does is look at all of Cauldron and go 'Fight me!' She copies Crawler, not just to survive the initial changes, but to mutate herself into something monstrous and unstoppable, even though that means stuff like melting off her own face, burning alive, and worse. She takes risks rather than holding to PtV's comfort, teleports, shuts Cauldron down, and focuses on and goes after Contessa specifically.
And then, when that's done, she focuses on the other Case 53s, starts plotting out how to help them escape, keep them together, and keep them safe. In the back of her mind, she's got lists of threats and enemies and they include names like 'The Protectorate' and 'The PRT' and a shit ton of other major groups. In front of her, she's got a bunch of super volatile mutated capes. And she wants to escape with them, keep them together as a group, and figure something out. Hit this point, this point, this point. Do this regardless of the risk. Mutate and break myself for the win.
You can't really say Brain would handle this in anything like the same way, because unlike Taylor's his crazy train has actual breaks--he periodically stops and goes 'Maybe this isn't a good idea' or 'Do I really need to do this?' Taylor...Taylor just kind of doesn't.