Paul "Jesus" Monroe gets a lot of love for managing to be both extremely badass and a genuine Nice Guy at the same time.
Axel and Tyreese are quite popular and very well-liked amongst the fanbase. The former due to having many funny lines and adding some humor to the series, and the latter for being a massive badass who at one point gets knocked down in a massive room full of walkers, only to kill them all by himself with only his hammer and without getting bit or scratched in the process. Notably, they are both among the very small amount of characters that Robert Kirkman actually misses and regrets killing off.
Alice Warren is one of the most liked female characters of the comic (along with Andrea and Michonne) for a variety of reasons, but mostly for being a very attractive and helpful nurse, as well as one of the only sane inhabitants of Woodbury. She later became a badass during the prison assault, and the way she went out was also remembered by many.
Morgan was a popular and memorable character despite appearing in just two episodes and a couple of Stingers prior to joining the main cast in Season 6, thanks in large part to his tragic backstory and Lennie James' excellent performance. Unfortunately, he became more of a Base-Breaking Character in Season 6.
T-Dog. While it's widely agreed that he wasn't as fleshed out a character as he could have been, fans like him for being a founding member of the Atlanta camp, an honorable Nice Guy, and for performing a Heroic Sacrifice to save Carol in Season 3.
Tobin for being a Nice Guy who is fully on board with Rick's decisions from the get-go, unlike many of the other Alexandrians. His status as one of the longest-surviving residents of the community has also turned him into a bit of Memetic Badass.
Scott has become a fan-favorite for being just a Recurring Extra, who is nonetheless competent and collected whenever we do see him do anything. As of Season 10 he is one of the longest surviving members of Alexandria, further endearing him to fans.
Bud, the spokesperson for Negan who introduces the threat of the Saviors. Despite dying within five minutes of his introduction he became an instant fan favorite, thanks to an awesome and charismatic performance from Christopher Berry.
Though widely disliked upon his initial introduction, Dwight has since become a popular character for his complex and compelling redemptive arc being near-unanimously considered one of the bright spots of the extremely divisive Seasons 7 and 8.
Simon, largely thanks to Steven Ogg's equally charismatic and threatening portrayal, with some fans going as far as to consider him to be more interesting and scary than Negan. Him disposing of the highly unpopularScavenger tribe in Season 8 certainly didn't hurt his popularity any.
Jerry became a fan favorite within minutes of his introductory episode airing thanks to being an AdorkableGentle Giant with cheesy dad jokes. His popularity likely played a role in him surviving the brutal annihilation of the Kingdom's militia in Season 8.
Dianne the Kingdom archer, for the same reasons as Scott. Like Jerry, she also survives the Kingdom massacre due to working with the Hilltop soldiers for much of the season.
Shiva is wildly popular due to being a damn tiger. Especially after her incredible Big Damn Heroes moment in the Season 7 finale. Many fans noted with heartbroken bemusement that they mourned the death of a CGI tiger more than some of the human deaths on the show.
Savior lieutenant Laura developed a following of her own for being a Punch-Clock Villain and then being among the few actively working to maintain the peace between the communities in the aftermath of the Savior War. Many fans decried her rather unceremonious death in "Stalker" and were pleased to see her return in flashbacks in "Here's Negan", in which she was revealed to have been one of the first Saviors as well as the one who gave Negan his infamous baseball bat.
An even more minor ex-Savior, DJ, also gained popularity when he was shown to have also undergone a HeelFace Turn in Season 9 and died trying to save the pike massacre victims from Alpha.
Dog, Daryl's Canine Companion as of Season 9 was immediately met with welcome arms, to the point that the mantra "If Dog dies, we riot" was adopted by the fandom. It helps that Norman Reedus had been pushing for Daryl to have a dog since as early as the third season.
Connie has become a fan favorite for being a level-headed, resourceful, and genuinely good-natured person, as well as a positive representation of a deaf character. Her interactions with Daryl have also turned them into a major Fan-Preferred Couple, with support for the pairing quickly rivaling that of the already popular Daryl/Carol ship.
Ozzy, the leader of the Highwaymen, was around for all of two episodes before being decapitated by Alpha and stuck on a pike. Despite this, fans took a liking to him almost immediately due to his quirky gimmick and his sense of honor. The fact that he bravely charged in to rescue the other pike victims who he didn't even know at great risk to himself certainly helps, though they all died anyway. Plus, he never got to see that movie.
Elijah, Maggie's masked, hooded companion from "A Certain Doom", due to the initial mystery surrounding his identity, his incredibly badass ninja skills, and his Big Damn Heroes moment saving Gabriel from some Whisperers.
Lucille. While she only appears in one episode, she's quickly become beloved for adding more depth to Negan, being a strong badass in her own right, and being played by Jeffrey Dean Morgan's real-life spouse, Hilarie Burton.
Omid is well-liked for being upbeat, friendly, and funny. Which is probably why he was the first to die in Season Two.
Pete became a fan favorite for being a strong and stern leader type, as well as being the only member of the Cabin group who was consistently intelligent and welcoming of Clementine. Many believe that if Pete had lived past "All That Remains"/"A House Divided", the plot wouldn't have turned so dark.
Walter was a beloved character in "A House Divided", because his level of kindness was a breath of fresh air after dealing with a group that locked Clementine in a shed.
Walter's boyfriend Matthew is in the same boat, resulting in jokes about how much he loves peanut butter.
Carver was quickly compared favorably to the comics' Governor and Negan... at least in Episode 2. His characterization shift in Episode 3 has been rather polarizing among fans.
Eddie from the 400 Days DLC, because his banter with Wyatt was so hilarious.
A New Frontier:
Jesus already had this status from both the comic and the show, but quickly became a hit in the game too, for his badass fighting moves, Nice Guy attitude, and being voiced by Garrus Vakarian.
Mariana Garcia. Players really enjoyed her adorkable and carefree attitude, many humorous moments and genuine kindness to Javi unlike the rest of their family. Naturally, they were not happy when she was unceremoniously killed off at the end of the first episode.
Conrad became well-liked by the fans after episode 2 in which he becomes determinant, because unlike every other Telltale game in which determinant characters tend to die quickly, not only can he survive several determinant deaths (thereby making him the first to survive so long) but his added depth, Character Development (unlike the rest of the new cast) and a fairly important role in the rest of the game has earned him a lot of love, perhaps even more so than the other members of the cast (excluding Clementine of course.)
On the other hand, there's also Violet. Other than being the first female LGBT character since Paige from Michonne, fans have taken a liking towards her for being a Defrosting Ice Queen, as well as also being a potential romance for Clementine.
James was an instant hit with players due to his past as a Whisperer, his preference at using non-lethal means to get rid of walkers, and the fact that he's played by Johnny Yong Bosch. People were hoping that he'd become another potential romance for Clementine before Episode 3, where he was confirmed gay.
Rosie the dog for being surprisingly sweet if Clem chooses to get to know her and for mauling Abel when he attacks Clem. The fact that, unlike most other dogs in post-apocalyptic stories, she survives in the end helps too. You can find several comments calling her best girl.