Is this bullying?

Wow Dude. You’re definitely a Bully and a horrible brother. Why would you do something like that to your own sister? That is beyond disgusting and disrespectful. You not only embarrassed her you invaded her privacy. I would be surprised if she disowned you because after what you did you sure deserve it. I sure hope she tells your parents and they tell you what a horrible and disgusting person you are.

Definitely bullying. To be honest, you're worse than a bully for that. Keep going, and you'll end up with a complete stranger for a sister.

I’m calling this rage bait.

Yes you are a bully.

Why are you showing your sister’s panties to people?

Yeah, you're definitely a bully dude. Not at all cool.

Maybe not bullying. But wtf, man, that was a shitty thing to do.

you are so insecure and broken deep inside that you had to embarrass your sister like that. You have nothing better to do than make fun of people