I don’t care how much you love Jamie and Claire together (I do too) but I think a love that passionate can make people unintentionally selfish and Frank Randall deserved a lot better than the treatment he got as an accessory to that. Imagine the love of your life disappeared without a trace and after putting your life on hold for three years they return completely changed and distant. Of course from Claire’s perspective this makes total sense as she has loved and lost and learned so much, but remember that Frank doesn’t have the virtue we as an audience do of witnessing all that. His world was turned upside down in 1945 and that happens all over again when he realises that even with Claire back in the 1940s in body, her soul will always exist elsewhere. In spite of this, however, he still offers to raise another man's child as his own, which Jamie himself wanted. He loves Brianna with all his heart as if she were his own, even though her mere existence is a permanent reminder of Claire's true feelings and infidelity. In fact Brianna, who could very well have inspired a great deal of bitterness and unhappiness within Frank, turns out to be the greatest source of joy his life has to offer. It is instead Claire herself who fosters Frank's unhappiness and heartbreak. It is for Brianna's sake he remains in an unrequited marriage, so is it any wonder he seeks out the affection of another woman who actually wants him? He could leave at any time but stays out of love for their daughter, the one person who loves him unconditionally, and who we know Claire never saw as Frank's. Then once Brianna is finally old enough to make her own decisions of who she would like to live with (which, incidentally, is not Frank forcing her to live with him but merely allowing her freedom of choice at last) and Frank is finally free to start living a happy life with those who actually love him, he is killed, finally freeing Claire from the prison she put herself in. So I will say it again... Frank Randall deserved better than the unhappy life he knew. He was a caring, loving man, who tried his best and sacrificed just as much as she did. Claire is understandably broken by the loss of her true love Jamie, but Frank never deserved that second-hand dissatisfaction that she foisted upon him. Sure, he made mistakes, but simply not being Jamie is not a character flaw. Tobias Menzies is, in my opinion, an exceptional actor who perfectly conveys the character's emotional complexity as he struggles through these latter years, and he will be sorely missed.