- The entire reason this show exists is because of Coulson's (former, because he now obviously is a main character) Ensemble Darkhorse status in the MCU.
- Antoine Triplett got a lot of love for being a really nice guy and for having nice chemistry with Simmons. Many fans were ecstatic when he joined the team near the end of Season 1 and essentially replaced Ward. Those same fans were outraged when the character was killed off during the Season 2 mid-season finale, only to become overjoyed when he returned during the Framework arc in Season 4.
- Season 2 notably introduced several characters who instantly became this, particularly Bobbi Morse and Mack, who got noticed by the writers who proceeded to upgrade them to main characters by the end of the season (Bobbi getting promoted during the winter break, Mack at the end of the season), taking them out of this territory. Bobbi in particular was set to get a spin-off due to the reception she got, similar to Agent Carter, though this didn't work out.
- Skye/Daisy's father, Cal Johnson. Thanks to him being a complex, Creepy Awesome character and Kyle Maclachlan's magnificent performance, every time he appeared on screen, you can bet the review and comments will be gushing about him and place him as the best thing in the episode.
- Raina has got a lot of attention from fans to her Affably Evil, Anti-Villain and Monster Fan Girl status, with many praising Ruth Negga's awesome performance. It's the point that in the 5th episode was renamed to 'Girl in the Flower Dress' from 'Scorch' because even the creators like her.
- Joey from Season 3, the Inhuman the team rescue in the first episode. Being a total woobie and realistic representation of what its like for a completely ordinary guy to suddenly get destructive powers they can't get rid of, as well as being the MCU's first openly/explicitly gay character, made him very endearing to audiences very quickly. It helped a lot when he reappears after having time to adjust, and is now very enthusiastic about being a superhero.
- Mike Peterson/Deathlok is pretty well-regarded by fans due to his tragic backstory, status as The Dreaded, and being a completely friendly Nice Guy who happens to be a cyborg super-soldier killing machine.
- Likewise, Yo-Yo Rodriguez, being an Inhuman with a really fun power (limited super speed), a great romance with Mack and a strong friendship with Daisy, and being the only Secret Warrior from the original comics (as well as the only one to stay on the show after the team breaks apart). She was so well-recieved she even got a spin-off mini web series that was highly regarded by the fandom.
- James, the Australian survivalist inhuman who just keeps getting more badass as the show goes on. There's a reason fans are hoping he joins the Secret Warriors as Lincoln's replacement. Subverted, though, with his FaceHeel Turn in Season 4, though some still love him for his Creepy Awesome portrayal.
- On the meta side, Kevin Tancharoen is highly regarded as one of the show's most gifted directors, and many fans get excited whenever his name appears in the credits as it inevitably means there's going to be some kind of extra-special set piece.
- Ghost Rider very quickly became one of the most popular characters when he joined the cast in Season 4. His popularity was so great that Hot Toys announced they would be producing a collectible Ghost Rider toy, making him the first character from the show's history to get an action figurenote .
- Jeffrey Mace, by way of Rescued from the Scrappy Heap. When introduced, fandom was against him thanks to him initially being described as an Obstructive Bureaucrat type who the team didn't trust, with many resenting him for replacing Coulson as Director. However, his Nice Guy demeanour, genuine respect for the team, his friendly interaction with Daisy, Coulson, and Jemma after they all resolved their initial distrust, lead to him winning over the fanbase, to the point his death was considered one of the saddest moments in the season.
- The three main recurring shield foot soldiers in Season 4, Davis, Piper, and Prince, have garnered a surprising amount of popularity due to their increasingly fleshed-out personalities, especially after they rather awesomely help Daisy and Simmons escape the LM Ds in Zephyr One and help protect them in the Framework. Davis even gets a Heroic Sacrifice to take down AIDA, though it doesn't take. Many fans were delighted when Piper and Davis returned alive and well in Season 5.
- The Doctor, Aida's Creepy Awesome second-in-command in the Framework AKA evil Fitz received almost unanimous acclaim among fans and critics alike for Iain de Caestecker's chilling performance and is widely considered to be one of the scariest villains in the entire show, if not the entire MCU. The fact that the two episodes he returned for (one in each season) after Season 4 were some of the best of their respective seasons did nothing to dispel that popularity.
- Though he was controversial in the first half, many fans warmed to Deke Shaw in the back half of Season 5, when he became an unexpected source of much-needed levity in a very dark season. Especially when it turned out that he was Fitz-Simmons' grandson.
- Enoch, the mysterious bald alien man in black from Season 5 erupted in popularity when it turned out that he was the Big Good of Season 5, and quickly won over audiences with a killer combination of The Comically Serious and Nice Guy, even more so following his Heroic Sacrifice in the mid-season finale. Naturally, the fans were delighted when he returned as a main cast member in Seasons 6 and 7.
- While some people thought that Arc Villain Kasius was boring, most fans agree that his henchwoman Sinara is incredibly endearing as a villain, due to her demeanor, cool telepathic spheres, the chilling musical theme accompanying her, and just Florence Faivre's performance in general.
- Rick Stoner, despite being nothing more than the voice of the Lighthouse's automated security protocol, is a massive hit, probably no doubt thanks to being played by the legendary Patrick Warburton.
- Glenn Talbot has became one of the more popular side characters, in large part because of his surprising amount of Hidden Depths early on — he was initially presented as an Inspector Javert and total Jerkass, but turned out to be a Reasonable Authority Figure — his nuanced Character Development into becoming one of S.H.I.E.L.D.'s biggest supporters, and his surprisingly close friendship with Coulson (after their initial mutual enmity). Taken to a whole new level when he became the MCU version of Graviton.
- Likewise, Talbot's bodyguard Carl "Crusher" Creel, the Absorbing Man, is difficult not to like after his HeelFace Turn despite his relatively few appearances. The fact he has a similar status in the comics also helps.
- Young John Garrett only appeared in the last four episodes of the final season, but he was a huge hit with for being an oddly charming Laughably Evil bad guy. The fact that he's played by Bill Paxton's actual son is the cherry on top, and many critics agreed that he absolutely nailed his dad's mannerisms as the character.
Ensemble Darkhorse / Agents of S.H.I.E.L.D.