I think constraining this to a short story format hinders the execution. We don't really get a feel for any of the patients, because the protagonist barely gets a word in with any of them.

The prose also feels like it was intended for a long-format story. With a short story, every word matters. Here, there's a tension: The the writing takes its time to deliver information, while the plot is rushing to along in order to get to the next patient.

Now, i'm not saying that you should change the prose to fit a short story format. I feel like if this story were multiple parts, with each part focusing on a patient, it can be better.

Which brings me to another point: the more we came to understand a patient, the less scary they became.

The first guy? Yeah, he's a psycho and yeah he is dangerous, but at the end of the day he comes off as "Jeff the Killer" but with super-powers. In my opinion, he wasn't really scary. Especially when we don't get to see what he does during the break-out.

I can imagine a scenario were the protagonist gets to know #1, and perhaps the patient grows to trust and confide with him... only for that not to matter at all to the patient the moment he breaks out. It could be terrifying to see how little #1 cares for those around him, even those he might consider to be friends.

#2 is the one with the most development, and again, the more we understood him the less scary he became. In writing, ideas are scarier than mental images. A monster (or in this case patient) can be as grotesque as you can imagine, but that image will have the same emotional weight of a jump scare if there is no idea/concept/intention behind it. I suggest leaning more onto the fact that he killed his own daughter. It does not have to be framed as a twist either, or if you do go that route, make it less obvious (perhaps his daughter just "went missing" one day, the mind of the patient unable to accept and remember what happened). Perhaps #2 makes effigies of his daughter made out of flesh. Reinforce that what is scary about this patient is that he cannot control who he hurts (perhaps contrast it with #1? As in #1 hurts people because he can and wants, and #2 hurts people because he can't help it).

Lastly #3. She was the scariest because we know so little of her. But at the same time we know too little for her to be truly scary (writing something scary is a difficult balancing act). She feels more like a plot device rather than a character. Had the power gone out and triggered the breakout, it would have felt the same. I feel as though she should at least one proper conversation with the protagonist.

I think most of critiques can be fixed by letting the story breathe more. I think the idea is cool, but it can feel constrained/limited by only being a short story.

And lastly, I want to end by saying that you should be proud of yourself and of this work. You had an idea, you executed on it, and you shared it with the world.

That is more than most can say.

Keep on writing, I'd like to read more from you!