Board Thread:General Discussion/@comment-26184894-20150518061700/@comment-24674051-20150519151458

300 Years of dark deeds are going to bite him harder than Ruby at night during a full moon. He is probably going to have nightmares for several YEARS of all the harm he's caused.

And even though Killian is on the Hero side of the ledger now, it will probably take some time for Gold and Killian to finally bury the hatchet (if they do ever bury it, which is still a distinct possibility that they won't). The animosity between these two runs deep, and as we were reminded during the frozen arc, actually extends back to before Rumple became the Dark One.