Every character on Star Trek: Deep Space Nine has moments of suffering, but Miles O'Brien seems to suffer a lot. There are more than a few episodes that are almost fully devoted to his torture, because he's just so human. When he suffers, we all suffer. That's the Miles promise!
Remember when he got put on trial by Cardassians for, checks notes, some bulls**t reason? Welcome to "Tribunal." How about "Hard Time," where he lived out a timey-wimey prison sentence and lost his nuts? Speaking of nuts, there's the episode where the O'Brien we follow for an entire story is actually an imposter ("Whispers") and he, naturally, dies. Then there's the time he made her ladyship slip on that bar of soap and lose her baby! Whoops, wrong O'Brien.
The suffering in Season 3's "Visionary" is a little light by comparison, but it does feature the show killing off Miles O'Brien for good. He's immediately replaced by a version of himself from a few hours into the future, but still. It was all Ronald D. Moore's idea.
Miles does some time-jumping and helps himself out in this episode, which means that Colm Meaney was acting with himself a lot of the time. It worked, because Meaney is amazing. Also on deck are some rowdy Klingon spies, a Romulan attack, the official hanging of the dartboard, and the entire station blowing up. Dabo!
Maybe he's born with it? Maybe it's the radiation. Welcome back to Warp Factor! Suffer through our latest episode right here.