In Fairy Tail, the story begins to establish couples early on in the story, rather than putting random people together at the end. This allowed fans to piece together who would end up with who, but the pairings were not always perfect. Gray and Juvia were one such couple. Although they did get a happy end together, the relationship was one-sided for most of the series.
Juvia's obsession, paired with Gray's constant rejection of her feelings, sometimes made it hard for fans to get behind the pairing. However, it's clear that they truly care about each other, going to extreme lengths to keep each other safe.
10 PERFECT: Juvia Is Happier Around Gray
Thanks to her water magic, Juvia spent a huge chunk of her life shunned by others since it always rained around her. People often commented on how depressing the rain was. It made sense that she would feel happy that Gray didn't seem disgusted by her magic, and despite the fact that she was an enemy at the time, he even saved her from falling. From that point, she changed from a depressed and reclusive girl to someone who is more happy and outgoing.
9 AWFUL: Juvia Gets Insanely Jealous
Whenever someone gets friendly with Gray, Juvia immediately considers them to be her rival in love. However, the women she proclaims are her rivals usually don't have a romantic interest in him. Lucy has gotten so many unjust glares from a jealous Juvia. Even Lisanna, who offered to help Juvia with her S-Class Mage Promotion Trial, was not exempt. Juvia's initial reaction was to consider Lisanna yet another rival in her quest for Gray's heart. Sometimes it's natural to get jealous, but never to Juvia's extent.
8 PERFECT: They're Protective Of Each Other
Gray and Juvia are often seen fighting together during major battles. When fighting the dragons, Gray doesn't hesitate to step in to help Juvia out, and during the Tower of Heaven arc, she is able to use her Water Body magic to hide him from enemy attacks. Despite starting off as enemies from different guilds, Gray and Juvia grow to trust each other with their lives and took time to hone their magic together in order to combine their spells into powerful attacks.
7 AWFUL: Gray Finds Her Creepy
Juvia makes many attempts to seduce or impress Gray, but they seldom work. She keeps changing her look in an attempt to find one that he would like and makes food for him that is actually shaped in his image. In the Grand Magic Games, Juvia uses a spell to earn third place in one round of the competition, declaring her love for him in the process.
However, the heart-shaped spell only managed to earn her a really grossed-out look from him instead. Until Erza told Gray that he owed Juvia a proper answer to her confession, Gray hadn't taken Juvia's feelings seriously.
6 PERFECT: Edolas Gray Is In Love With Edolas Juvia
Although Edolas seems to be the opposite of Earth Land, the regular Fairy Tail world, the story establishes that it is simply different and not necessarily the opposite. This is proven by how Mirajane remained exactly the same, and Edolas Wendy looked far older than Earth Land's Wendy. In both worlds, Bisca and Alzack Connell are also in a relationship. This, along with the fact that Edolas Gray loved Edolas Juvia, meant that there was a chance that Earth Land Gray would be able to love Earth Land Juvia.
5 AWFUL: Waiting In The Rain
In the Avatar arc, Gray leaves Juvia without an explanation as to why. This leaves her so confused and depressed that it begins to rain again. She is so attached to him that she waits in the same place that he left her for six months. Juvia even stands in the rain to the point of giving herself a fever.
To be stuck in a depression for half a year makes Juvia look helpless without him, and it makes Gray look like an awful person. Since he did it for a mission, he would probably do that to her again if the need arose.
4 PERFECT: Dual Self-Sacrifice
During the Alvarez Empire arc, Gray and Juvia are controlled by Invel Yura's Ice Lock spell and forced to fight each other against their will. Using what willpower they can muster up, they both decide that they would rather take their own lives. They do not hesitate to try to spare the other, but Juvia planned ahead with a blood transfusion magic that she learned ahead of time, saving his life. This makes Gray become emotionally unstable for a period of time before he discovers that Wendy arrived in time to save Juvia's life.
3 AWFUL: Juvia Forced A "Love Potion" On Gray
In Juvia's early days in the Fairy Tail guild, she was so determined to get Gray's love that she was willing to purchase a love potion. She wanted to use it to force him to fall in love with her, but needless to say, that's morally wrong. Thanks to karma, the potion was not really a love potion, and it made Gray think of the first person he saw as his rival instead.
This left Juvia feeling dejected, but Gray still had it much worse. He went so far as to declare the horizon to be his rival before running miles away from the guild.
2 PERFECT: Living For the Ones You Love
When fighting with Meredy, Juvia's life becomes connected to Meredy's and Gray's. Meredy attempts to take her own life in order to kill Gray as well, but Juvia embraces her and pleads with her to live instead. Rather than just begging for her own life, Juvia shows concern for Meredy's as well, saying that Meredy needs to live for the people she loves. Falling in love with Gray made Juvia adopt similar ideals to his, and it also made her connect to others easier, leading to one of the most heartfelt moments in the anime.
1 AWFUL: Juvia's Obsession
Juvia is absolutely obsessed with Gray, to the point where she spends a huge portion of her time following him around and watching him from some sort of hiding place. When he asks her to do something for him, she doesn't hesitate to do it to the best of her ability. She even goes so far as to chase Meredy with a broken leg by crawling. Anything that involves Gray immediately catches her attention, and if someone threatens him, she flies into a frightening rage.