Cedric Diggory
"Kill the spare." Voldemort gave the order to Wormtail.
Wormtail is the one who killed Cedric.
Bertha Jorkins.
Her "shadow" came out of Voldemort's wand during Priori Incantatem.
Voldemort killed her, unless he loaned his wand to Wormtail but that seems highly unlikely...
Explanation for Horcrux.
Now I'd be the first person to admit, and LL can vouch for that😊, that I don't take everything at face value but the only explanation that makes sense of how Voldemort unknowingly turned Harry into a Horcrux is this:
"Dumbledore took a deep breath and closed his eyes.
'Tell him that on the night Lord Voldemort tried to kill him, when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort's soul was blasted apart from the whole, and latched itself onto the only living soul left in that collapsing building. Part of Lord Voldemort lives inside Harry, and it is that which gives him the power of speech with snakes, and a connection with Lord Voldemort's mind that he has never understood. And while that fragment of soul, unmissed by Voldemort, remains attached to and protected by Harry, Lord Voldemort cannot die.'"
~Excerpt from P686 of "Harry Potter and the Deathly Hallows" USA, First Edition.
Generally speaking one cannot create a Horcrux simply by killing, "there's a spell" as Horace Slughorn puts it that needs to be said to do such a thing. Though, apparently there are special situations as evidenced by Harry the Horcrux explanation above.
hmm jane u r right
cedric was killed by wormy and voldremort wud never give his wand to anyone
and bertha was killed by voldemort according to priori incantem
and ur other theory is also making sense
there is spell to make horcrux otherwise those who killed they cud hv made horcruxes too
like bellatrix she killed sirius
u explained well