It's fine.
You can't stop giving consequences for bad behaviour just because they find it difficult to control. That doesn't help as it just makes them think it's acceptable, which makes it even harder to control. It also feels unfair to siblings if you are still holding the siblings accountable for their behaviour and not the possibly-ND child.
What you have to do is understand that giving consequences is not going to teach him to change the behaviour, so don't expect them to, and don't increase them because they are "not working". You need to work on the skills with him at a different time, when he is calmer. You might need to control the environment more, which might mean closer supervision and a lot of inserting yourself between the children or steering him away from his brother when he's in that more wound up state, so he can't hurt him - this is you helping him to control his impulses, so he doesn't do something that would get him into trouble. It can also help to ask everyone to pause when you can see a situation heading towards a danger zone and then be a go-between.
With possibly-ND children it does not usually work to let the siblings try to work it out between themselves. You can pause them both if you catch it early enough, and manage the interaction ie "translating" behaviours like snatching or shouting into the information that the 2yo needs: That 5yo would like a turn, and model how for 5yo to ask nicely.
Or sometimes I would stop the 5yo ideally before he could snatch, and bring him to the side, validate his frustration, and explain that there are three choices: He can ask 2yo for a turn, he can find something to do while he waits for 2yo to get bored, or he can wait for a time period I deem appropriate, and then I will enforce a turn if 2yo is not yet finished with the toy (which I will inform 2yo of if he chooses it). I wouldn't say it in that many words. I'd say something like "Your choices are, ask DS3 for a turn, wait for him to finish, or wait 5 minutes." If he chose to ask him for a turn, I would remind him that DS3 is allowed to say no, and then he has to wait, but only 5 minutes. Then I would help him wait if he needed me to by suggesting other things we could do for 5 mins and holding him on my lap if necessary.
Or if I had anticipated it early enough I might even be able to intervene before the 2yo "claimed" the first turn, anticipating that they would both want a turn at once, and be able to manage that decision so that they both have input into making it, but I'm there to keep things cool and help prevent it turning into a panic grab/snatch moment.
Yes, this is all very helicoptery, but for some children, they need this kind of explicit step by step teaching of how to handle this exact situation right now in the moment they are encountering this exact situation, because role play doesn't cut it as they forget in the adrenaline rush of the moment, and they don't work it out by trial and error, because they never get a chance to reflect on their own actions, because they shoot right up from "Not fair, that's mine, I must get it back" to a complete overreaction/panic response like violence or OTT screaming, and then in return the other child will often either thump them back or an adult will intervene and they will be whisked away which just increases their sense of not fair/panic - and by the time they have calmed down they have no idea what even started it in the first place, and have not practised any better responses so the exact same scenario will play out the next time it comes up.
You might need to be more proactive in terms of noticing when his energy level is getting more frantic and abort the mission before it gets to that point, which allows you to frame going home in a more positive way rather than as a punishment. You might need to be much more on top of structure and expectations than other parents are, making sure you are offering frequent snacks, drinks and opportunities to use the toilet or get physical exercise or have quiet time, whichever are the needs he tends not to be aware of for himself. If he struggles with sensory needs those might need to be taken into account as well.
If consequences are actively making the situation/behaviour worse, then you might want to consider whether they are causing more harm than good and whether you need to adjust approach, but in general, totally dropping them is a bad idea. You want to keep (fair, proportionate, clear) consequences but try to work with your child to help them avoid the behaviour which will lead to the consequence, rather than saying well it's not fair that they get into trouble because it wasn't their fault, but also rather than just leaving them to predictably make the bad choice and then say it was their own fault they got into trouble, if that makes sense? It's not their fault if they are ND, but they do have to learn what behaviour is acceptable or not regardless of it, and the adult bears some responsibility as well for keeping in mind whether they are realistically able to cope with a situation or not, and offering support when necessary as much as is possible. You don't have a crystal ball obviously, and you can't predict everything all the time, but IME you start to get a very good spidey sense of when they are about to kick off, so you can intervene early a lot of the time, or proactively plan ahead a kind of risk assessment of OK, we have a day at home/at the park - what situations are likely to cause issues here, and think about how to manage them and what support he might need from you. And all of this is exhausting, so any support you can access at all either for yourself or for him, grab it with both hands.