Considering Agents of SHIELD deals with aliens, time travel, and artificial intelligence, it makes sense that the main characters would want some kind of normalcy. The relationships between characters often help the audience better relate to those on-screen, even if they can't always relate to the situations they find themselves in.
SHIELD featured several relationships, with some having a greater impact on audiences than others. While most ended in death or betrayal, there were others who were able to make it to the end - much to the fans' pleasure.
Ward And Daisy
Upon first becoming an agent, Daisy was assigned to be trained for missions by Grant Ward. There was a clear spark between them that seemed like it would develop as the series went on. However, that all changed after Daisy learned that he was actually a double agent for HYDRA.
During all their encounters after the revelation, it was obvious that Ward was still interested in her while she hated him for betraying the team, causing the potential relationship between them to never be fully explored. The closest fans came to seeing them in an actual relationship was when Daisy was put into the framework, where she was dating him in an artificial reality where he was still a double agent, but for SHIELD.
Elena And Keller
After Mack became the director of SHIELD, he called off his relationship with Elena so that he could better focus on his new position. During that time, Elena began a relationship with one of the organization's newer members, Damon Keller. At first, they did their best to hide their relationship but Agent May figured it out and advised Elena to pursue it.
Keller later went to make Mack aware but Mack also revealed that he already knew and fine with it. Unfortunately, the relationship had a tragic end when Keller's body was taken over by a shrike, causing him to project crystalized spikes from his body and forcing Elena to kill him to protect everyone else. It was a little disappointing that the show cut this relationship as they did seem to make each other happy.
Simmons And Will
At the end of season 2, Agent Simmons gets swallowed up by the space monolith, which transported her to the Alien planet of Maveth. While there, she met Will Daniels, an astronaut that was sent to the planet as an unknowing sacrifice for the entity that lived there.
Will helped her better understand the environment and let her stay in the underground living space he had inhabited. As they spent more time together, the closer they became, their relationship became romantic. However, this came to an end when Simmons was saved by Fitz and Will ended up being left behind. When the team went back for him, they discovered that his body had been taken over by Hive when he helped Jemma escape. Simmons was devastated by the news.
May And Andrew
Andrew Garner was a SHIELD agent that was happily married to May for years. However, after the incident in Bahrain, the couple ended up getting a divorce. Garner reunited with May when he came back to help SHIELD as a psychologist for the Inhuman patients before leaving the organization again.
After surviving a difficult mission, May called Garner and the two began taking steps to restart their relationship, with May even suggesting that she would retire. However, their relationship faced another struggle when Andrew was exposed to Terrigen Mist and became Lash, an Inhuman designed to kill other Inhumans. After the team discovered this, Garner spent most of his time in containment, helping the team every so often before sadly being killed by Hellfire.
Coulson And Rosalind
Rosalind Price was the leader of the ATCU, an organization created to help deal with the new Inhumans, which led her to meet Agent Coulson of SHIELD. While the two agencies started out as opposing forces, they eventually formed an alliance and began sharing information.
Despite never fully trusting each other, Rosalind and Coulson began seeing each other for a while. However, while the pair were having dinner together, Rosalind was sniped and killed by Ward under orders from Gideon Malick. Rosalind bled out in Coulson's arms and her death motivated him to eventually murder Ward.
Lincoln And Daisy
Lincoln was an Inhuman Daisy met while at Afterlife and was tasked with helping her adjust to her new powers. After the war between the Inhumans and SHIELD, Daisy returned to SHIELD while Lincoln tried to start a new life as a doctor.
Daisy convinced him to come with her so that SHIELD could keep him safe and he later started being trained by May, joined the Secret Warriors, and started dating Daisy. However, their relationship came to an end when he sacrificed himself to destroy Hive by launching them both into space, on a quinjet, with a nuclear warhead. His death was seen to affect Daisy in the long run.
Coulson And May
Coulson and May have known each other since their early days of working for SHIELD and often going on field missions together. While the two clearly always had feelings for each other, their relationship only started to be explored when the team was being replaced by Life Model Decoys of themselves.
Agent May was one of the first to be replaced and her LMD revealed her true feelings for Coulson, and the two started their relationship after escaping from the Framework, confessing their love for each other. After learning that Coulson was dying, May decided to retire alongside him in the season 5 finale, staying with him in Tahiti all the way up until his death.
Daisy And Sousa
In the final season, Daisy Johnson met fellow SHIELD agent Daniel Sousa while on a mission in 1955. While she didn't initially tell him why she and the team were there, he was eventually taken from the timeline and joined them. The relationship between the two officially started when Sousa revealed his true feelings for Daisy in the time loop episode when she woke up to find him waiting by her side while she recovered from the experiments ran on her by Nathaniel Malick.
Sousa is extremely caring and their dynamic manages to work despite them being from wildly different time periods. The series ended on a positive note, with the couple still going strong and exploring space together aboard Zephyr Three.
Elena and Mack
Elena Rodriguez was one of the New Inhumans and first met Mack when the team was investigating the weapons that were stolen from the police. Mack attempted to apprehend her, believing her to be a criminal. However, he soon found himself held captive before he was rescued and she was brought back to SHIELD by Daisy.
After some time, she became an agent and joined the Secret Warriors, with Mack giving her the nickname "Yo-Yo" because of her powers. After battling Eli Morrow, they began dating and she even entered the framework to save him and chose to stay behind in there with him after he refused to leave his daughter, Hope. While they did temporarily break up when Mack became Director, they ultimately got back together and are shown to still be in a relationship by the end of the series, while still working for SHIELD.
Fitz and Simmons
Out of all the relationships, the one that has been at the core of the series has been between Agents Leo Fitz and Jemma Simmons. Although they initially met each other at the SHIELD Academy, they wouldn't find themselves in a real relationship until years after they joined Coulson's team.
After years of the pair repeatedly being separated from each other by time and space, they continually found their way back to one another. They later got married by Coulson in season 5 and would end up having a daughter, Alya, named after Jemma's favorite star. Following their final mission with the team, they retired so that they could spend more time together as a family.