Sawyer/Kate well, technically I am glad that they didn't end up together in Jack's! wet dead dream, but however, all the final was such a crap that this two being a part of it already makes me cringe. They deserved way more than that and the writers just cheapened their love and their story. I will never be able to not see them as true love, because they where willing to die for each other and it is the purest form of love ever.
Harry/Luna their connection and understanding was incredible. Luna was the only person who could make this misereable boy happy, she brought back his hope when he was ready to stop fighting, she felt him and knew him better than any of his frienRAB who had spent years by his side. I will never be able to get why JKR didn't make them a couple and they will always be my biggest disappointment ever.
Freddie/Effy even with them ending on Effy choosing Freddie in every way and telling him she loves him and Freddie protecting her till the very end I am still mad that Freddie's character got this kind of an exit. Even though FE is one of my OTP's but I cared about Freddie's character more than about this couple as much as I might love it and I would have prefered to have them broken up (but of course still in love because this kind of love can never die) than his character getting such a horrible exit and no closure at all. Out of all the Skins characters, IMO, Freddie deserved a happy ending more than anyone else.