Juno despises Hercules since he is the result of Jupiter's actions. He is also quite powerful, and she is unable to get rid of him. Jupiter is Zeus' and Hercules' father. Juno attempted to destroy Hercules while he was still a newborn. However, Athena intervened and saved his life.
As soon as Hercules reached puberty, he went after Juno to avenge his birth mother's murder. During their fight at Olympus, they both used their powers every which way they could but neither one could defeat the other. In the end, Jupiter came down and stopped the fight because he didn't want either of them to be killed. He then told them that if they wanted to kill each other then he would not stop them. So they fought again, this time with no rules and no boundaries. Finally, Hercules won and killed Juno.
Hercules then decided not to go back home because he thought that Jupiter had abandoned him. This why people say that gods are cold-blooded monsters who will do anything for attention. If you cross them or piss them off then you will get your heart ripped out of your chest.
However, what everyone doesn't know is that after Juno died, she became a star and named Vega II. Every six months, she dims slightly and fades away completely until next year when she does it all over again.
Hera despised Heracles/Hercules because he was born to a mortal woman (Alcmene in this case), whom Zeus, her husband (and brother), had impregnated. She, on the other hand, had a vendetta towards Hercules for some reason. Perseus, on the other hand, was not targeted by Hera, nor was his mother, Danae. However, both of them did experience problems with their spouses who were siblings. Perseus' father, Acrisius, refused to let him marry his daughter until he came out of the tower where he had been confined by his grandfather, Zeus.
Acrisius thought that if he locked his son up in the tower he would be safe from any danger. But Zeus didn't want anyone to know he was creating people so he decided to release Acrisius from the tower in order to get him out of the way. This is why Perseus's marriage to Danae was problematic because they were cousins. But again, neither of them were targeted directly by Hera.
As for Heracles/Hercules, he felt betrayed by Hera after she helped Zeus bed her own sister, Metis. This is why he went against her and helped Alcmene give birth to her children. He knew that if Zeus wanted him dead then there would be no hope for him to escape being killed. So, in order to protect himself and his family, he had to defeat Zeus and remove him as an enemy.
Even before he was born, Hercules had opponents. Hera, Zeus' wife, fell into a furious frenzy when she learned that her husband's mistress was pregnant. When her stepson was a young adult, she performed a spell on him that momentarily rendered him mad, causing him to murder his beloved wife and their two children. Later on, when Hercules sought revenge against his mother for her role in the death of his family, she fled from Olympus.
Hera also took advantage of the moment to curse her stepson with many burdensome tasks. To escape this punishment, he left Greece for a time but later returned when he realized what had happened to his wife. However, even after killing his mother, Hades would not release him from his contract so he could join his wife in the afterlife. Only when Zeus intervened did Hercules find peace again. In return for saving his life, Zeus allowed him to marry Hebe, one of his daughters.
Hera's actions may have been motivated by jealousy but she also knew that if Hercules succeeded in all his endeavors, they would never be able to overcome him. Thus, she tried to prevent him from forming any more relationships by spreading rumors about him. If he married, they would always be divorced before too long. This way, he would be unable to build a stable family life and she would still be able to torment him even though she was dead.
This was due to Hera, Zeus' wife, knowing Hercules was her husband's illegitimate son and wishing to eliminate him. She sent the Erinyes (Furies) after him, who were able to find him wherever he went. Fearful for his life, Hercules returned home to Mycenae where his family had moved after leaving Tiryns. There he killed Zeus in revenge for killing his father.
Hera also sent a plague against Greece to cause death and ruin, but Hephaestus saved them by making the Greeks chariots out of the skin of the ox that had attacked Heracles. These made him invincible against other gods and humans until he left his weapon of choice up to this day: the bow and arrow.
After killing Zeus, Hera sent another plague against Greece and this time Heracles was not able to save himself or anyone else. Only Athena brought him back to life. It is said that if you ask three people what role Athena played in saving Hercules from death, you will get three different answers. This shows how popular belief has changed over time regarding her involvement with the story.
Athena gave Hercules two bolts from her own head to use as weapons.