I was a terrible bully to my INTP younger sister when we were kids. We get along pretty great now, though. To my knowledge, my sister has never been a bully to anyone but has been bullied at school. I have terrible self-esteem because all throughout elementary school (and middle school--my school was a k-8) I was, for reasons literally unknown, ostracized by 95% of my grade. I was never confronted or directly bullied. It was mainly... laughing and whispering behind your back, mocking, teasing, and avoiding me. It absolutely did not help that because of my peanut allergy, I sat at my own lunch table in the corner of the cafeteria, almost ALWAYS alone (a special "allergy kids" table they made us sit at). Things got better around 8th grade when my friends started sitting there with me, and when I entered high school where there were new people who hadn't met me before, things got better. But elementary school was absolutely terrible for me. To this day I have no idea why I was ostracized like that. The only people who would allow themselves to be seen with me were the "misfits" and "loners" or people who just didn't give a shit about their "social image". And those friends are wonderful people who I still have in my life today. But because of the way I was treated, I'm nervous, shy, and timid around people I don't know. I constantly long to have more friends (especially since all but 2 now live in other cities for college), but I'm too scared to meet new people. It's easier online, but even then, I sometimes have difficulty.
And the weird thing is, people see me as a generally nice person. At work, customers tell me I'm the "nicest" and "most helpful" employee they've ever met. At work and back when I was in college, I'd get along with everyone great, students and teachers alike. But it's not like we exchange contact info or hang out. This was especially bad at school--be friendly with people all semester, new semester comes around and I never see them again. One time I was brace enough to get someone's contact info, but I rarely ever talk to them because it's like I don't even know how to "make friends" anymore because of what they did to me back then.
It's a kind of weird feeling and hard to explain, since it wasn't confrontational bullying. I was never physically attacked, and the worst that happened was the occasional (rare, even) "snob" coming up to me during recess and teasing me, which I was slow to catch on to because I'm a kind of naive and gullible person. I have not made a single "close" friend since junior year of high school--which is about 4 years ago now.