It is rare that I say this, but "Hard Time" is an episode that outstrips all but one of the episodes of Babylon 5.
As a series B5 is far superior in writing and content, but this single episode of DS9 just blows every other episode of B5 away (the finale excepted)
Miles is forced to live 20 years of prison in half an hour -- it is burned into his memory -- and he comes back to DS9 suffering from PTSD and is a changed man. He is angry, and he goes through a very tough adjustment.
spoiler
It builds up, getting worse and worse, until a truly heartbreaking scene where he nearly hits his daughter just because she wants some attention.
You can see the pain -- the horror -- on his face when he realises what he has done, and he walks out because he knows he is a danger to Molly and to Keiko.
He then goes to a docking bay, and picks up a phaser, with the intention of blowing his head off.
Colm Meany excels himself -- it is the high point of his role (odd as it sounds) -- and given that it is a stand alone episode, outside of any plot or story line, it is just amazing.
I haven't seen any other episode of any other series -- British or American or anything else -- that has matched this. And given it is Star Trek? When you compare and contrast it to TNG and Voyager, it is beyond belief.
I cannot praise it enough. And this, and Pale Moonlight, are what make DS9 the best of the Star Trek shows, for me at least.