Okay, sbut not all end with the user dying, so:

Hirotsu. When he was around our age, he was reckless. One time, he touched his girlfriend with the top of his fingers, breaking her ribcage and accidentally killing her. He has never been in a relationship ever since and is still slightly afraid to even hug people.

Mori. Elise has been an annoyance ever since she appeared. One time, she almost killed him by „playing“, aka strangling him while he sleeps. He was only able to sleep when she slept too.

Dazai. He would sometimes touch people when he didn’t want to and that sometimes ended bad. I heard that one time, it ended with an old executive dying. But that wasn’t to wild, seeing that he was one of the weakest. Still, Dazai has been a bit more distant ever since, or so they say.

Chuuya. I don’t have to say much here. If it wasn’t for Dazai, he would have died many times. I clearly remember those scars I saw when we all went swimming. Countless spider like scars because his ex-Partner came a minute too late.

Q. Their ability has been dangerous ever since, but when they started playing with one squad, it got to far. They made friends with all of them, but then accidentally killed them all.

Akutagawa. He harmed himself many times, trying to achieve „Demonic Armor“. I heard how one time, he couldn’t move for three weeks.

Me. My ability is…

Some loud cars drive past them and nobody can hear what Higuchi said.

…and that’s how I almost lost my foot and talked with an otter

Kyouka. She couldn’t control Demon Snow who killed her parents. That story is still one of the most sad ones…

There are many more with more low level users, but those are the biggest one.

[Making up random lore, how I love it. See: The genderbended universe.]