It really, really depends on the full chart and other influences in their life like their general stress level because if their life is very stressful, their reactions might be more intense than someone who isn’t experiencing a lot of stress.
Generally though, frustration is really hard for Capricorns because when they’re frustrated it usually means that something is out of their control.
It could be frustration with a loved one, or that they can’t help a loved one, or just frustration with school or work, but it usually comes down to not being able to fix something or someone or prevent something from happening, or something along those lines.
Frustration can even lead to desperation although it might appear as anger to people who are less in-tune or just don’t know him/her well.
Capricorns don’t tend to get mad often, they internalize, so they’re more prone to depression than anger. If you do piss them off to the point of real anger, it can be scary. It’s like an explosion because all of that internalization has just been unleashed.
If you hurt a Capricorn, that’s a different story because Capricorn’s are all about trust. If you break it, you might have lost them forever.
If you hurt them, that means they cared deeply about you. I’ve noticed that if a stranger says something rude or mean to a Capricorn or says that they don’t like him/her, it doesn’t really phase them because what matters most is the people that they love and respect. If a stranger doesn’t like them, who cares?
They don’t know or respect that stranger and that stranger doesn’t know them so it’s much less hurtful to them. So if they’re truly hurt by someone, it’s a big deal because that means that they really loved and respected them.
It could definitely lead to depression and isolation and a loss of trust with that person. Even if they do forgive you, it won’t really be the same for them. You know that saying, “Fool me once, shame on you. Fool me twice, shame on me.”? Well, I’m pretty sure that was a Capricorn.
They won’t forget because they don’t want you to be able to hurt them again.
That’s without factoring in the person’s individual Mars & Moon and other placements that might affect how they react.