Why did this guy who didn't know me really hate me?

[Anonymous]

I'm a shy and quiet person but a lot of my friends say I'm nice

[thomual]

There could be a lot of reasons. Details are required. Often it's just the look of a person. If you scowl a lot, are unusually ugly to him, are overly attractive, or friends with an enemy of his, these could explain it. But without details, it could be anything.