I think cannonicaly cybertronians cannot cry, they are physicaly unable to. So imagine tarn the first time he cries. Maybe it's because of something in the past, unalbe to cope with the stress of the hole situation or cause of an emotional overload. Reader would eighter keep a distance or cradel tarn to them
I ended up going a little silly with this one lmao
Tarn has been gone an unusually long time. Usually he’s threatening to kill you or whatever, but somehow he made it off the table. You were afraid he’d somehow gotten into the vents or disappeared somewhere else, you didn’t doubt his ability to actually harm you, but the faint sounds of sniffling lead you to a different conclusion.
In human culture, crying is typically seen as weak. While Tarn doesn’t exactly know this, he didn’t want you to see him leaking whatever was coming out of his eyes. His face felt hot and his nose was dripping, absolutely disgusting. He couldn’t control what was going on with his body, not even the noises that he was making.
You found him in a cabinet you’d apparently left slightly ajar. His overall demeanor was still the angry ball of hate it usually was, but now he was more vulnerable than ever. You couldn’t coax him out. He was the one to start up a conversation.
He asked what was happening to him. You told him the truth. “They’re tears”, you said, “humans usually get them when they’re really sad or really happy… and I don’t suppose you’re very happy.”
“This is disgraceful. Disgusting.”
“Yeah, well, it’s natural.”
“Not for me, not for a cybertronian!”
“Shut it, you insolent organic piece of slag!” More tears poured from his face. You got the feeling this level of emotion wasn’t normal for him. “When I get back into my body, I swear to primus I will tear you limb from limb, and I will make it as painful as possible. I won’t stop until this miserable planet is dust.” He looked angry, but only for a second. His words hitched on sobs and cracked in pain. He tried his best to put on an intimidating persona, he did everything he could to scare you off, but he was too small. Too weak. You just stood there staring at him.
If he still had a spark, it would be aching. He felt his world shatter and with it the remainder of his composure. Tarn lost it. He cried. Hard.
No matter what he threatened you with, he still needed help. And when he was done crying that’s what you would offer him. That’s all you could do, really. Maybe one day he’d come around.