When you get right down to it, Hitch is an amazing friend.
Hitch says “I’m the only real friend you’ve got left in this town.” This is a double whammy; it means that Hitch has stayed friends with Sunny despite the growing conflict of interest it represents, which also means that other ponies have cut ties with Sunny over less. Watching as an adult, you can appreciate that Hitch holds all the power in the relationship, and that Sunny needs him more than he needs her. Yet he never tries to take advantage of her.
In his conversation with Sprout, Hitch rants about how he’s done bailing Sunny out. But I noticed something about Hitch’s line in Zephyr Heights:
“Arresting you. And… saving you… A bit of both, actually… You’re welcome!” He said he was done, yet he’s travelled across Equestria and infiltrated a (supposedly) hostile city. He’s annoyed at himself, because despite everything that’s happened, he’s still there for Sunny.