This week's trope: Death Of The Hypotenuse!
"Alice, Bob, and Charlie are in a Love Triangle. Alice loves Bob, but also has feelings for Charlie — or maybe she doesn't, but can't or doesn't want to turn him down (maybe she's even in a relationship with or married to Charlie while pining after Bob). However will she resolve this dilemma? Well, fortunately, she doesn't have to — Charlie meets with a convenient illness, accident, or other such fatal situation, freeing Alice up to go after Bob without guilt. If Charlie is aware of Alice's feelings for Bob, he may tell her with his dying breath that she shouldn't mourn him too much, because he wants his beloved to be happy.
This trope is where The Plot Reaper meets Cleaning Up Romantic Loose Ends. If Charlie's death is not so accidental, it's Murder the Hypotenuse or The Uriah Gambit, depending on whether it's done directly or set up indirectly. See Comforting the Widow. Compare to Ship Sinking. May still be a Bittersweet Ending and even lead to Dead Guy Junior."
First off, I love the name of this trope. Second, you don't get much more deus ex machina-y than this. Third, I kinda love this trope.
What better wait to get rid of an annoying third wheel who's come between two people who, dangit, really ought to be together?
Oh sure, you could have one of the members of the couple do the noble thing and merely break it off with the hypotenuse (see: Anne Shirley and Gilbert Blythe), but why be reasonable, when you can instead have a good old-fashioned massacre?
Don't get me wrong. I don't think death is necessary. Take The Wedding Singer, for example. In that film, [Robby and Julia meet, and are destined to be together, but are with other people. Soon after, Robby's fiancee lets him go. Later, we learn that Julia's fiance, Glen, is a cad. Robby woos Julia, they fall in love, and Glen gets shoved into an airplane bathroom by a beefy guy out to protect Billy Idol and a flight attendant. Everybody wins!]
So there are ways around it.
But death, why, it is quick and clean.
Well, no, it isn't. And actually, it's pretty shameful. It's like, Really, writers? Is this the best you could do?
I refuse to reference Downton Abbey again. But those who have seen season two will know who I'm talking about. Oh, all right, fine, I'll talk about freaking Downton, but I won't name names! [So. Downton. One of the hypotenuse deaths this past season only caused more problems for the couple, so that one can be excused. The second death in season 2 -- well, it seemed to cause problems (one of the members of the A-couple felt overwhelming guilt over the hypotenuse's death, and declared that he and his love could never be happy because of it.)] But one episode later, they'd pretty much thrown that out the window and were all XOXOX. Blame the hormones, I guess.
And Rest In Peace, poor, expendable Other. :(