Mark seemed to be protective of Victoria. When she was sent to the Parahuman Asylum, he chose to go with her, rather than go with Carol to see Amy off, after an argument between them. He visited Victoria more often than Carol. After recovering, Victoria seemed to be generally closer to her father than to her mother.
Mark tried to be a father to Amy, but his depression kept getting in his way. Though Amy recognized his efforts to be her father, she was nonetheless distant from him, feeling that Victoria was her only true family.
As Flashbang, Mark wears a white costume with padding and helmet - the costume is marked with a green-yellow grenade icon. The costume's armor panels, mask, straps, and guards were styled like a grenade's exterior.
Out of costume, Mark is generally fit, and he looks younger than he actually is. As of Ward, he had short hair, and had beard stubble with some white hair that gave away his age.
Mark's power allows him to create bouncing orbs of light that can detonate either concussively (and largely nonlethal) or explosively with potential lethal force. He can adjust the charges to control the size of the resulting explosion and maintains a secondary power that allows him to ignore the effects of his own improvised weapons. He could create a large amount of explosions.
He was severly devastated by a brain injury, but was able to get around it thanks to Panacea's intervention.
24 days after the Battle against Leviathan, Mark was still laid up in bed due to a head injury. When Bonesaw and her creation Hack Job came to try and recruit Panacea, the killers injected acid into Mark to get force his adopted daughter to heal him. He had an argument with Carol when both of their daughters were sent off; eventually, Mark accompanied Victoria to the Asylum in Pennsylvania, while Carol went with Amy to see her off to the Birdcage.
"There was no long-term, and trying to cling to one would only spoil it all."
This article contains spoilers regarding the ending of Worm and plot of the sequel.
He ended up separated from his wife; while Carol lived in a house, Mark lived in an apartment with Victoria. At a reunion barbecue for the Dallons and their extended family, he was told of Amy's presence beforehand, but later tried to warn Victoria about her sister's presence. However, following the reunion, Victoria refused to go back to his apartment.
He later apologized for the incident at the reunion, and offered advice to Victoria regarding her team. Victoria later used some of his spare costume materials when making her own.
↑ 1.01.1He was forty-two but looked younger. The fact that he was as fit as he was played into it- only the white in his beard stubble really gave it away. His hair, too, was short. He was the only one who hadn’t put a sweatshirt or jacket on, owing to the proximity of the two heat sources- he was wearing a t-shirt that was form-fitting in a way that showed off his muscles. Pretty darn gross, given he was a dad, my dad, and he was supposed to dress his age. I would have insisted on clothes that hid any sign of muscle at all, really, had I been given a say. - Excerpt from Daybreak 1.7
↑ 2.02.1Mark had tried to be a dad. He’d made her pancakes on the weekends, taken her places. But it had always been inconsistent. Some days he seemed to forget, others he got upset, or was just too distracted for the trips to the ice cream store or mall. Another secret that the family hadn’t kept – Mark was clinically depressed. He had been prescribed drugs to help him, but he didn’t always take them. - Excerpt from Interlude 11h
↑The door had been left open, at my dad’s insistence. One foot tucked under me, I’d snuck my one foot across the bed until I could touch Dean’s knee, trace my toe along his leg. Seeing if I could break his focus enough to make him mess up while reading aloud. - Excerpt
“He exchanged words with her in her cell this morning. He decided it was more important to accompany Victoria to Pennsylvania.”
“I didn’t realize that was today. If you’d asked, I could have rescheduled Amy Dallon’s departure.”
“No. It’s fine. I prefer it this way.”
“You didn’t want to see Victoria off to the parahuman asylum?”
“Victoria is gone. There’s nothing of her left but that mockery. Mark and I fought over it and this was what we decided.” - Excerpt from Interlude 15.x
↑“They came a lot,” I said. “I know that. My dad more than my mom. But every missed visit was a horrible thing, and the little things mattered so much when I had nothing else. Um. And this basketball game, I know I’ve talked about this before. But this one girl kicked my freaking ass. In my face, knocking me over, intercepting every pass, blocking every shot. She didn’t have any powers or anything, she was just… good. Better.” - Excerpt from Daybreak 1.8
↑Treating like a monster might be a little overboard, but they're accurate in reading scenes where Amy was neglected.
Carol's word choice is one hint here - you can read the interlude that was just covered and note how Carol refers to Amy vs. how she refers to Victoria. The words aren't hateful, but Amy is 'amy' and Victoria is 'my daughter'. She says, outright, "I don't want her" while the child is in earshot, and then when Lady Photon says "You could grow to love and trust that little girl, too.” Carol's (later, connecting) thought is "Liar".
Look at Amy's conversation with Gallant... "Carol never really wanted me. Mark is clinically depressed, so as nice as he is, he’s too focused on himself to really be a dad."
Interlude 11.h, It had always been Victoria, only Victoria, who made her feel like she had a family here.
Then later, same interlude, What Amy felt from her ‘mother’ was a chill. She knew that she was only justifying the darker suspicions Carol had harbored towards her since she was first brought into the family. It was doubly crushing now, because Amy knew about Marquis. Amy knew that Carol was thinking the same thing she was.
Carol didn't reach out, she wasn't warm, she wasn't a mother. At best, Amy was a person living in their house. At worst, Amy was someone suspicious, Marquis' daughter. So Amy never really had a 'home', a safe haven to retreat to. If you want to read between the lines, the fact that she'd go out at night to visit the hospital (and that nobody was stopping her) might indicate more about her feelings at home. She wasn't mistreated. She got fed, she got clothes. Mark (Flashbang) even tried to be a warmer dad when he was up to it, but that's something as rare as the sun coming out in the UK - brief and unpredictable bouts of good in the midst of a perpetually overcast setting. In the end, all she really had was Victoria. - Comment of RPR.net by Wildbow
↑ 7.07.1Flashbang, Mark Dallon – Husband to Brandish, father to Glory Girl and Panacea. Could create bouncing light orbs that detonated with concussive or explosive force. Suffered long term head injuries in the Endbringer arc, but was cured by his daughter. Wears a white costume with a green-yellow icon of an exploding grenade, complete with padding and a helmet. - Cast (in depth)
↑ 8.08.1“Spare stuff from dad,” I said. I pulled out some equipment. It was the right kind of material, all in a matte gunmetal, but the texture was all wrong. Dad was ‘Flashbang’ and the armor panels, mask, straps, and guards were all in the style of a grooved grenade exterior. - Excerpt from Shadow 5.6
↑ 9.09.1Flashbang – Member of New Wave, Flashbang can create orbs of energy that bounce and explode with a measured degree of light and power. - Cast (spoiler free)
↑ 10.010.1Mark flicked his eyes in one direction, offered the slightest of nods, his forehead rubbing against hers. Amy flung herself to one side as Mark stood in one quick motion, flinging the glowing orb at the little girl.
Hack Job flickered into existence just in time to have to orb bounce off his chest. It exploded violently, tearing a hole into his stomach and groin. The villain flew backward, colliding with Bonesaw.
But two more copies of Hack Job had already appeared, and the scalpel spiders were responding to some unknown directions, leaping for Mark and Amy.
Amy grappled with one spider, struggled to bend its legs the wrong way, cried out as the scalpels and needlepoints of the other legs dragged against her skin.
A blast sent her tumbling, throwing her into the couch and dislodging the spider. Mark could make his orbs concussive or explosive. He’d hit the spider with the former, nothing that could seriously hurt Amy. She climbed to her feet, picked up the oak side-table from beside the couch and bludgeoned the spider with it.
More explosions ripped through their living room as Mark continued to open fire, hurling the orbs with a ferocity that surprised Amy. When Hack Job tried to block the shots with his bodies, Mark bounced them between Hack Job’s legs, off walls and off the ceiling. Almost as if he could predict what his enemy would do, he lobbed one orb onto the couch. It exploded a half-second after one of Hack Job’s duplicates appeared there.
More duplicates charged from either direction, and Mark dropped a concussive orb at his feet, blasting himself and one of the duplicates in opposite directions. He quickly got his footing and resumed the attack, fending off one duplicate that turned his attention to Amy, then going after Bonesaw.
Bonesaw had retreated into the hallway that led into the bedrooms at the back of the house, the basement and the kitchen at the side. Mark threw an orb after her, obliterating the hallway, but Amy couldn’t see if he’d struck home, not with the clouds of dust that were exploding from Hack Job’s expired duplicates. Between the time it had taken to create the orb, throwing it and the lack of a scream after it had gone off, Amy knew Bonesaw would have gotten away. -Excerpt from Interlude 11h
↑Mark was in the living room, sitting on the couch. No longer able to don his costume and be Flashbang, Mark could barely move. He had a form of brain damage. It was technically amnesia, but it wasn’t the kind that afflicted someone in the movies and TV. What Mark had lost were the skills he’d learned over the course of his life. He’d lost the ability to walk, to speak full sentences, hold a pen and drive a car. He’d lost more – almost everything that let him function.
What little he regained came slowly and disappeared quickly. It was as though his brain was a shattered glass, and there was only so much he could hold in it before it spilled out once again. So they’d patiently worked with him, helping him to hobble between the bedroom, living room and bathroom. They’d worked with him until he could mostly feed himself, say what needed to be said, and they didn’t push him to do more.
Victoria was in costume as Glory Girl, but she was unclipping a bib from around his neck, something to ensure he didn’t stain his clothes while he ate. Amy’s adoptive father turned and smiled gently as he saw the other two members of his family. It was all Amy could do to maintain eye contact, smile back. -Excerpt from interlude 11h
↑Brandish shook her head. “I… you know I never planned to have kids?”
“I remember you saying something like that. But then you had Vicky.”
“I only caved to having Vicky because Mark was there, and I had to think about it for a while.” - Excerpt from Interlude 15.x
↑“Heroes, like the PRT, and like my family’s team, followed, to try and keep the peace until things settled. My family’s team was Lady Photon, Manpower, Flashbang, Brandish, Lightstar and Fleur.”
“The heroes without masks,” Ashley said.
“Yeah,” I said.
“I remember them. I was one of the villains who flocked,” Ashley said. - Excerpt from Flare 2.5
↑The bystanders began filing away as their destinations were called out. I was surprised to see New Wave among them. Brandish said something to Panacea, squeezed her hand, and then turned to leave.
Had they retired? Given up on fighting? Or was this simply a fight on a scale they weren’t prepared or able to participate in? - Excerpt from Extinction 27.4
↑He looked relaxed though. As relaxed as I’d seen him in a while, really, and I’d seen him passed out on the couch back at the apartment.
I was aware that my mom had seated herself so that two neighbors sat between her and my dad. Where my dad had dressed in a t-shirt and sports pants for the occasion, she had dressed up. Just a bit of lipstick, her hair short and styled, a ruffly sort of white blouse and pencil skirt. She’d kicked off her shoes earlier in the evening, leaving them beneath her chair.
I was aware of the distinction in how they’d dressed, too. In another time, before everything, there would have been more… connection, I supposed. Each influencing the other, until they matched more. - Excerpt from Daybreak 1.7
↑In the background, my dad was trying to get my attention. He’d sat up, and didn’t look relaxed anymore. He offered me a small smile. I acknowledged him by lifting one hand up from where it sat on my elbow, in a mini-wave. - Excerpt from Daybreak 1.7
↑Point_Me_@_The_Sky: I absolve you on the condition of one get together where we have some good eating, your treat, and you need to let me know if you hear of any good apartments or things because I am not good going back to my dads - Excerpt from Daybreak 1.8
↑He took a seat on the armrest of the armchair, one foot on the ground. “I want you to know that what happened at your mom’s house, I’m sorry about that. It wasn’t right.”
“I appreciate that. I… I wish I could tell you that I was sorry for how I reacted there. But I don’t know if I can.”
“I wouldn’t ask you to,” he said. “I think any and all of us should be understanding when it comes to old wounds.” - Excerpt from Glare 3.5