Kinda meant to showcase how much of a dumbass he is, but when Nick gets bitten by a zombie at the beginning, all he does is apologize for screwing up Juliet's birthday while she cradles him in her lap.
Near the end, Juliet's dad accepts Nick as his daughter's boyfriend. In his own way.
Gideon Starling: Nick, you may not be the kind of guy I'd pick for my daughter, but she's definitely the kind that would pick you for herself. And she's always been a hell of a lot smarter than me!
The good ending. Everyone sits down to celebrate Juliet's birthday while pleasant music plays in the background. Nick's present for her is a box of lollipops hidden underneath roses. Looks like everything is gonna be alright after all.
Using a Nick Ticket. Juliet takes Nick in her hands, says something affectionate to him, and gives him a kiss on the forehead.
And then uses him as a weapon...
Juliet downright refusing to leave a cynical Nick at the beginning of the Cathedral level.
Juliet: I'm not going without you! I love you!
If Juliet's health is depleted but you have a Nick Ticket, it can be used to revive her. Instead of collapsing, Juliet falls to her knees. Then Nick, with his body, runs over and helps her up. It's especially sweet to hear how worried he is.
Doubling as a Tear Jerker, all of Nick's lines if Juliet dies. They really show just how much he loves her.
Juliets reason for decapitating Nick and resurrecting him is this, even if it is a little selfish. She just couldn't stand to see him die and wanted to make sure he stayed alive. Unfortunately, we know what that meant.