Pele - the Hawaiian Goddess of Lava is known for her fiery temper. She fell in love often and most of those young men were not fortunate to escape with their lives. The incredible details of some of the stories is what really makes her special.
In one story Pele throws Lava at her Lover, her own favorite little sister, the sister's House (forest, actually), and sister's Best Friend for good measure. Because she THOUGHT the Lover and Sister may like each other, when in reality they were both loyal to Pele. (They bonded because of this trauma and proved Pele right. Irony Burnnn) The Other Wiki tells the tale.
Also another unfortunate young man that Pele fell in love with was already in a happy relationship, and had no intention of cheating on his girl, even with a Goddess. Pele was not impressed by his moral fibre. Story of Ohia and Lehua
Dido in The Aeneid. When Aeneas leaves Carthage, Dido curses him and all of the surviving Trojans, then commits suicide. It bears mentioning that said curse involves damning their two future nations to constant savage bloodletting.
There is a Japanese folktale concerning a woman named Kiyohime who, when rejected by the object of her affections, a monk who took a vow of celibacy, turns into a dragon and incinerates both him and herself when he tried to hide from her underneath a giant bell. More information can be found on The Other Wiki.
The huldra of Scandinavian folklore are a type of fairy who appear as beautiful women with cow or horse tails. Although they are often eager to marry, they are also very strict and demanding, and if you even think of turning one down, she will kill you.
The story of the 4 winds in Lakota mythology. They were all in love with the goddess Wohpe. She chose the South Wind, because he wasn't so vocal about it. The North Wind tries to steal her away from his younger brother every winter. The North Wind is represented by the color white, and the South Wind is represented by the color red.
In Classical Mythology, Persephone turns a nymph into a mint plant, and then stamps on her, for daring to flirt with her husband Hades. The weird thing is that Persephone originally ended up as Hades' wife when Hades captured her and forced her into marriage, so it must take some extreme Stockholm Syndrome for her to not only grow to love him, but to become jealously protective of him. Although besides kidnapping and tricking Persephone (a by product of which is causing winter to happen) Hades has never done anything all that bad. In some interpretations of the story, Persephone always loved Hades, and the kidnapping was staged because Demeter would never let Persephone go
The most famous example from Classical Mythology would be Hera, wife of Zeus. Half or more of the myths about her and about the only thing she is remembered for is pursuing horrible vengeance on the lovers of Zeus and their offspring. (Zeus being by far the most powerful of the gods, there was nothing she could do to harm him directly.) The worst acts were probable against Lamia and Hercules. Hera either stole or in the worst stories forced Lamia to kill her own children turning her into a monster. The latter she tormented his entire life in one way or another, but the worst would be inflicting madness on him causing him to murder his own family. The 12 Labors that made him famous were ironically for a crime he arguably had no control over. She seemed tolerant of Ganymede, however. She apparently stops trying to torture Heracles after he dies, ascends to full godhood and marries her daughter, or at least there are no myths telling of it. But would having Hera as a mother-in-law really make things better? Probably not.
Cole's note version: Hera is Juno in Roman Mythology. Juno is the name and character basis for Yuno.note AKA, one of the major inspirations for the modern name of the trope. The letter j is pronounced like the English y in most European languages.
Medea of Greek myth is a scary one: when Jason left her, she burned her rival alive with a fire so intense it set on fire the royal palace, set on fire the city of Corinth for being ruled by the man who got Jason to dump her, and killed her own children to end his line (A Fate Worse Than Death for the ancient Greeks). Note that this is the Corinthian-backed version: more ancient and less known version have Medea less genocidal and just burning her rival and the royal palace, and setting the city on fire only when the Corinthians killed two of her children for being her unwitting accomplices.
Some interpretations of Paradise Lost posit that Lucifer is basically the greatest yandere of all times, unable to suffer the knowledge that God would rather be loved by a fallible, mortal, corrupted humanity than by the Morning Star himself.