In the past, Elizabeth was never King Liones' true daughter, but it is believed that he loved her as his own. This is proven when Elizabeth climbs onto a tree to get her father attention and he desperately tries to get her down from it despite not knowing how to climb. This caused him to fall and hurt himself. This shows that he cared for his daughter very much, even though they are not blood related.
When Elizabeth offers herself for Meliodas' safety in the first chapter, she kept on crying, saying that Meliodas was being too kind to someone he doesn't know. This was something that Meliodas completely disregarded as he protected and saved her from Twigo. Later, when Meliodas invited Elizabeth to travel with him, she happily accepted.
When the townsfolk were upset at a young boy for pulling a prank on a Holy Knight Gilthunder for insulting their ale. The village leader was the only one who stood up for him, saying that the boy protected their pride, which not of the others had done and worked together to remove the holy sword to restore their water supply. Despite not moving the sword at all, they showed that they cared for one another and worked together to return their pride.
After seeing Meliodas again since the last time ten years before, Diane was overjoyed and started to cuddle him, showing that she cares for and loves Meliodas.
Elizabeth became depressed after Meliodas got injured and the doctor who was supposed to help him was forced to kill Meliodas instead. She blamed herself for the whole ordeal because she made Meliodas and the doctor get involved. However, Meliodas told her that she should stay strong and even told her that even if she died, he will continue to stop the Holy Knights in her place.
After Elizabeth saved Meliodas and Diane from Ruin's illusion magic, Meliodas went to her and said that he accepted her will and went on to fight Ruin. During the fight, Meliodas defeated Ruin and said that there is no way for him to escape since he hurt someone important to him, and that was his sin.
When the petrified Ban was left behind by King, the spirit of Elaine came to Ban and set him free with a kiss. This shows that Elaine still loved Ban even in death.
Despite leaving her alone for the past seven hundred years, Elaine was still shown to believe in King and told him to protect Ban.
Even in death, Ban still swore to make Elaine his, which made her happy.
After being (temporarily) shrunk down to normal human size, Diane wanted to get the affections of her one-sided crush in Meliodas. This is played for laughs as she asks him to grope her like he does Elizabeth. He declines, stating that he'd never do that to her because he cares too much, as she starts to tear up, clearly upset, he tries to cheer her up by rubbing the top of her head, something he could never have done previously and her appreciation is clear to see.
Even after hearing Meliodas said that he doesn't fondle anyone important to him, Elizabeth stated that she will still believe in Meliodas no matter how he sees her.
In Chapter 39, When Cain asked again if Meliodas really destroyed Danafall, to which he told him he didn't betray anyone, Cain then started crying and hugged Meliodas, being glad that he didn't betray anyone they care about.
As Elizabeth was forced to return to Liones with her sister Veronica, an injured Meliodas got up and stood between them, stating that he will protect Elizabeth with his life.
It was shown again when Meliodas' broken sword was stolen, Meliodas didn't seem to care much about it and also revealed that if Elizabeth was all right.
In Chapter 46, when Veronica sacrificed herself to save Elizabeth from Geera's attack, she stated that despite them being not blood related, she still loves Elizabeth as a sister.
During their training, Ban revealed to King that he is planning on getting a magical item from Liones that could speak with a Goddess and ask them to revive Elaine. This shows that Ban really want Elaine back if he is going through the trouble to ask for a deity help.
In the same chapter, King mentioned that Meliodas could be a demon himself, but Ban grew furious and threatened King for saying such a thing about Meliodas. Ban then went on saying that Meliodas and Elaine were the only two people to accept him for who he is which no one had ever done. He even believed that Meliodas is too kind to be a demon, which shocked King.
Despite being a cruel woman, Guila shows a lot of love toward her younger brother, Zeal as she killed his bullies and sworn to do everything she can to make him happy.
She even makes a Heel–Face Turn and helps Diane after the latter protected Zeal. Hell, Diane ruining her chances to escape for saving a child she doesn't even know (when she previously had said she didn't care about humans) is this. And Zeal being the sweetest little brother ever.
When Gowther saved Pelio from an attack from the Armor Giant, it shows that despite being emotionless, he shows a lot of care toward his young master who saved him in the past.
While Diane was wondering if Meliodas would ever make a upset face if she was kidnapped like Elizabeth, King told her that he would definitely come for her even if he does it alone which made Diane happy, but wonder if he does it to cheer her up.
As Diane was fighting against Dreyfus she was gravely injured and could barely fight, but all she cared about was to save her friend Elizabeth.
To note out that at first Diane didn't like Elizabeth because she was close to Meliodas, but doing the series, she grew to like and respect Elizabeth as a friend of her which is rare for Diane since she think nothing of all men beside Meliodas and dislike any female that are close to Meliodas. It shows that Diane truly cares for Elizabeth.
Guilthunder being finally able to help Meliodas after the latter killed the chimera keeping Margaret hostage. He even cries while he thanks Meliodas and calls him his hero.
Arthur's cheerful hero worship for Meliodas. Especially because is obvious that Merlin had a hand in it.
King Bartha has several of these:
His reunion with Elizabeth. Pure fatherly love.
He doesn't only rescue Threader, he gave him a name, taught him how to live in society and give him the best job Threader could ask for. Threader's Undying Loyalty is obvious but we see how much Bartha cares about him when Threader risks his live trying to open the charmed door and Bartha begs him to stop before he kills himself.
His friendship with Arthur is very cute too. The young man remembers him fondly and goes all the way to his kingdom to rescue him.
Dreyfus arriving in the nick of time to help his son (who is obviously happy to see him again) to fight Hendrickson
This is more a Tear Jerker, but Ban desired to bring Elaine back to any cost proves his utter devotion to her. The Tear Jerker part is what he has to do to resurrect her and he obviously is broken for it but he'll do it anyway.
Gustav showing his concern for his sister despite being previously an asshole to her. He even begs Ban not kill her. Props to Ban too for really find a way to recover Jericho alive.
When Merlin's not being shady and doing things for the lulz, she's pretty much this.
After all the insanity dies down thanks to Hendrickson's defeat, King encounters Diane, who had been shrunken down to human size with some magic pills. She then asks him if he'd like to spend some time with her. He declines at first, saying he doesn't want to be a third wheel since he figures she wants to use the opportunity to hang out with her crush, Meliodas. She then makes it clear that Meliodas won't be there, and she wants to go out with him.
Escanor writing a sappy love poem for Merlin and her genuinely wanting to hear it. Keep it mind that sort of thing seems utterly out of character for her.
In Chapter 124, Hendrickson had been shunned in his youth due to this 'Acid' power. Dreyfus took him in, and they became good friends. Dreyfus even held his brother in high regard, despite his jealousy. Even when Fraudrin possessed Hendrickson despite Dreyfus' immunity, Dreyfus immediately gave himself up without hesitation to save Hendrickson.
Jericho bluntly telling Elaine during a heated argument and battle as the former has the latter pinned down, that even if Ban doesn't return her feelings, she would never hurt him or cause the kind of pain Elaine inflicted due to her enhanced jealousy by her curse. Elaine is visibly stunned by this. Doubles as a Tear Jerker.
The bar Escanor runs is named 'My Sweet Gluttony.' It's rather obvious who he was thinking of when he came up with the name.
Although brief, Ban and Escanor's reunion, with Escanor being relieved to hear that they are heroes again. Ban then immediately trusts his life to Escanor despite it being night.
Meliodas and Ban's reunion in chapter 159. After they have there usual contest Ban expresses regret over trying to kill Meliodas but Meliodas pays no mind and acts as if it never happened.
When Elaine and Elizabeth meet up, they become fast friends, despite teasing each other about their respective love interests.
King's will to protect Diane is enough to both allow him to overcome the previous Fairy King's doll and make her realize the depths of his devotion to her, despite her amnesia. This, in turn, allows her to empower her Harlequin golem to the extent that it knocks Dolor's on its ass.
"You are not the person that would walk alongside me... when i was drowning in in absolute darkness, she always the one who illuminated the path of my life, because that is what a sun does."
A villainous example, the relationship between Monspiet and Derrierie is one of the most close-tight between the Ten Commandments. They're always together, she is more open with him, and he even provides a  for her. It's specially visible when Meliodas is about to use Revenge Counter on all Commandments during their fight, and Monspiet embraces her to protect her, with Derrierie looking quite sad, as if she knew it was hopeless and they were about to face certain death. Thankfully for them, Estarossa stops the technique.