When Characters have bad days

Recently, in one of my works in progress, I came to the realization that something terrible had to happen to one of the characters.  Like I said in my Facebook post, I'm not going to give out details to avoid spoilers, because this was a real punch in the gut.  Part of the reason why is this:  I don't want to needlessly make a character's life difficult.  If something this terrible is going to happen, I want it to have meaning to the story.  Basically I want the character's sacrifice to be  worthwhile.  This means the scenes involved have to be treated with respect, which in turn tends to slow down my writing.  As some of you may have read in previous entries, I disagree with the idea of just torturing characters to make a story.  Adversity is what makes a story/character progress, torture is disrespectful to the reader.
One of the more interesting ways I've had to approach this is with Hero Unit.  My main protagonist, Ace, is very similar to Superman, in that she in incredibly powerful, but unlike Superman, no one knows her weakness.  (For fans of the series, yes she has one, and no I'm not telling you what it is yet).  When you have an indestructible character, who is also more powerful than everyone else, the approach has to change.  A lot of the adversity for Ace comes from the fact that she is law-abiding.  As a Registered Exceptional, and EED hero, there are a number of restrictions placed on when, and how, she can use her powers.  Add to that the fact that she understands just how much more powerful she is than everyone else and suddenly this immensely powerful individual has her powers restricted at nearly every turn.  Because lets be honest, how boring would it be if she just did everything, and was never challenged at all?  My books would be a lot shorter, that's for certain.
Then there is her PTSD.  Rarely do we get a chance to see how a character's actions may come back to haunt them.  Mostly we don't really see what happens after it's all said and done.  Rarely does an author revisit the same characters once a story has been told.  One example I do like is in the Marvel Cinematic Universe.  Tony Stark is driven by the horrible things that have happened to him, from Iron Man, all the way up to the up Infinity War, he's been fighting a reactionary battle, often with himself.  It was emphasized in Iron Man 3 (no negative comments please).  He is not a soldier, he's not been trained and yet he's put himself in that position, and as a result he has to deal with the memories, the stress it's placed upon him.  It affects all of his relationships, his daily interactions.
Ace was a soldier, but she's had to do some pretty terrible things.  She enlisted right out of high school, so she was still a teenager when she was deployed.  One of the things I haven't gone into very much, is how unstable to world still is post Exceptionals War.  There is a lot of unrest, and often the US military is called on to deal with it.  In her brief time as a soldier, Ace had to do a lot, and to this day the memories still haunt her.  These memories can come to the surface at any time, though there is usually an event that triggers them.  Working as an EED hero exposes her to more chances to experience triggering events.  These are also scenes that I have to treat with respect because PTSD is a very real condition that soldiers have to deal with. 
So there's another look behind the curtain, if you will, of the writer.  I am by no means suggesting that every one who writes stories is like me.  These are just my thoughts/processes.