This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Ask That Guy with the Glasses
His response to "why does Daddy hit Mommy?" is just a little too close to how Domestic Abusers think.
Due to Harsher in Hindsight (in the episode he acts like it's just a joke, but later episodes show he really is that broken and he dies alone), the venting in episode 14 about how lonely he is.
In episode 23, Ask That Guy ripping into his Child by Rape who wants to see him again.
ATG: Truth of the matter is... [in angry tone] I was raped. She forced me to swallow a case of viagra, shoved me onto her body and made me thrust over and over and over. It was a horrifying experience that I will never forget. And you were a mistake. A horrible mistake. And in answer to your questions; why did I run away? Because I was scared shitless. Where's your child support? I spent it all on hookers. And why did I put you up for adoption? Because abortion was too expensive. I don't love you! And whatever hell you have to face in the afterlife is too good.
In episode 33, the description of his parents. They make everything worse, they're ridiculously controlling, they tell him he's not manly enough and also that they found him in a garbage dump and should have left him there.
It probably helps if you're a fan of the book, but his quoting of the Happy Place George gives Lenny before he kills him is really well done.
Poor GPS. She got proposed to, then had her marriage fail, then when she thought they were going back to being friends, got shot.
In episode 50, the narrator sobbing pathetically when Ask That Guy leaves after an argument. Ends up surprisingly heartwarming though.
In 58, when asked if he's the president for the hair club for men, he pulls his hair obviously expecting being able to do something, and screams in pain that he's so stupid.
Sitting on a Trauma Swing with the halves of his pipe still in both of his hands. You almost want to give him a hug.
Especially if you watch early episodes beforehand where he's all calm and collected, seeing him break so bad under the "true or false" question later is incredibly unsettling.
There's something really raw about his self-hating "you're a grown man now!" rant.
Speaking of self-loathing (anyone who has had mostly abusive relationships will understand what it's like to be confused at someone who actually does love you), a few episodes later we have this:
ATG: Ohh, now I can live a blissful life without the narrator. *immediately eats his gun*
Caption: It's been decided that this ending is far too depressing to be shown on DVD. We present to you this substitute.
*ATG then crushes a random puppy first, and afterwards sodomizes it with his pipe.*
Caption: Fuck it.
Episode 62's rampant humiliation. Technically he had it coming, but it's still uncomfortable to watch. Not even Critic had to stoop that low.
Also, when the normal music doesn't play, crying for his mommy when all she's done is treat him badly.
When he uses reverse psychology on all the hipsters telling them to "not shoot themselves" and they all do so, he declares he loves his job, however, when he's then asked the question "Do you love your job?" He suddenly breaks down in distraught tears showing he feels genuinely guilty that he just made a bunch of people commit suicide and declares he doesn't want to live. Then he goes back to being his calm and collected self saying every once in a while he does have a real human emotion, but he'll always kill it with hatred.
When they heard second-hand that Rob said (for the given reason or not) that Ask That Guy was only coming back after a long time gone to finish properly with a “finale arc”, the fangirl tears flooded tumblr.
His actual death is very Dropped a Bridge on Him (which is heartbreaking in of itself) and just a way to move the site but he goes back to his old location to do the finale episode and actually has affection for it. It's really sad in a nostalgic way.
That nobody really talks about it – Doug even still introducing himself as being known as Ask That Guy in cons – is depressing as well.