The entirety of Ben's speech to Adam at the end of Iron Kissed. Right up to and including the part where he risks his life and his standing within the pack to help Adam see what's going on in Mercy's head... and reveals his own past history of being raped as a child to do so.
Stefan, coming to see Mercy at the end of River Marked to deliver a gentle asskicking because she's ordered all of the wolves away, keeping them from taking proper care of her.
Made all the more heartwarming by the fact that she basically did the same to him in the beginning of the book.
Kyle staying by Warren's side even when the latter has turned into a mindless animal due to severe injuries. That, and the fact that Kyle stubbornly stays with Warren despite discovering the horrors of the supernatural world (and despite the hostility of the other werewolves), eventually convinces most people that he has more than earned the right to be Warren's mate.
Goes both ways. Mercy notes that for Warren in that state to have not harmed Kyle (except for a few scratches when Kyle impulsively tried to help subdue him) speaks deeply of their bond.