Dawn's Relationship History

Xander: The memories manufactured by the monks gave Dawn a long history of having a crush on Xander, which fed Xander's ego muchly. When Dawn developed a crush on Spike, instead, Xander's self-esteem took a blow.

Spike: Dawn had a crush on Spike for a while, and frequently went to his crypt to hang out with him and hear scary stories about stuff he did when he was evil. Dawn was one of the first people to realize that Spike was in love with Buffy, however, so she knew she didn't have a chance with him. Instead, they developed an increasingly strong friendship founded on mutual respect and acceptance. Spike doesn't treat her like a child, and she doesn't treat him like a pariah.

Kevin: Dawn had a crush on Kevin Berman, some kid in her art class, but nothing ever came of it. Just as they were starting to really talk to each other, Buffy arrived at Dawn's school to tell her that their mother had died. Kevin sort of paled in importance after that, I suppose.

Justin: Dawn and Janice went on a double-date with cutie-pies Justin and Zack on Halloween night. Dawn really liked Justin, who seemed like a sweet guy, and they even kissed (Dawn's first kiss, in fact) ... but it turned out that Justin was actually a vampire, and in the end Dawn staked him.