Killing the love interest is right out of the BONANZA playbook. It's a tired trope. I toyed with it and dropped it.
Well, I completely disagree. A story where a secondary character is introduced only to die at the end can bring out tremendous insight into a primary character.
I give you this exemple:
I usually dismiss about 95% of all TNG episodes as merely adequate writing-wise (sorry), but this episode and especially the performance by Michael Dorn was cinema gold. And made me a fan of Dorn's.