Mr. Worf from Star Trek: The Next Generation has long been a fan favourite. The first Klingon in Starfleet, serving on the Federation Flagship, Enterprise-D, who went on to become the Tactical Officer (whatever that is) on Deep Space Nine, and then back to the Enterprise-E for the movies because reasons.
He remains one of the more complex characters of the franchise, an honour-bound man who would rather throw himself on the pyre than risk the Klingon Empire or the Federation, a man of reserve but passion, father of a unknown son, a lover of prune juice. But he was also a man of many loves, most of whom fell under some rather gruesome ends. Was Worf an innocent bystander... or a black widow in disguise?
Worf was introduced as a random button pusher. I honestly don't know what his job was and I don't even care to look it up because season one suuuuuucked! In the episode "Second Skin," however, Tasha met a sudden and senseless death at the hands of some creature made of cough medicine and blank printer's ink. Actually.
Now granted, Worf wasn't on the scene but as luck would have it he got an instant and bafflingly unprecedented promotion to Security Chief, having shown no predisposition to security detail before. Suspicious...
She later returned with a little surprise, their love child Alexander who was an insufferable weiner comparable only to Wesley "Shut Up Wesley!" Crusher. During some complicated and clandestine Klingon plots I won't get into, she was murdered, leaving Worf with a dead girlfriend and unwanted son he shipped off to his human grandparents in goddamn Russia! Cold, Worf.
This was explained away that he was a grieving widow and a there was no place for a child on the ship, despite the absolute zoo of kids roaming the hallways. Innocent enough but could Worf perhaps be a bit miffed his lady friend tossed him aside, birthed an unwanted child, and dragged him into boring Klingon politics? So miffed, in fact, he resorted to murder most fowl?
Troi managed to survive this courtship, unlike poor K'Ehleyr, but in the series' final episode "All Good Things" a possible future is presented where she had died prior to marrying Worf. This future never came to pass but the question remains, how did she die exactly? Natural causes or perhaps a jealous and notoriously violent lover?
The typically stodgy Worf quickly began a long and very entertaining courtship of wild child/old soul Lt. Jadzia Dax. She was a Trill, a joined species where Jadzia was a young scientist while a centuries-old slug named Dax shared its memories and living space in her stomach. It's weird but awesome.
Unlike prior relationships, Worf managed to wed Jadzia but, wouldn't you know it, she died at the end of season six! They managed to save the space slug at least and it was transferred to newly-dubbed Counselor Ezri Dax (again with the psychologists). Skipping the grieving widow stage, Worf kinda tried to mack on her too but, new to this joined species/sudden rush of past lives' memories bit, Ezri was having none of it.
After Deep Space Nine wrapped (and possibly missing the opportunity to murder Ezri), Worf returned to the Enterprise... likely to finish the deal with Troi! Luckily, she came to her senses and ended up marrying Riker/blueballing Worf.
Now it could easily be argued that Worf wasn't present in any of these deaths but having watched a handful of To Catch a Killer episodes, I'm pretty much an expert on setting up a hit. You don't do it yourself; you arrange for others to carry out the dirty work for you. Worf's many loves/career blockers generally died as plot advancements but the body count is just too much for any one man over the course of ten years.
They could have been plot advancements... or perhaps the master plot of a deranged and murder-fueled Klingon. You decide!