Warning! SPOILERS ahead for The Walking Dead season 11 episode 7.
The Walking Dead season 11 is finally introducing the most hated character from the comics: Sebastian Milton. Season 11 has had three main storylines to cover in its first seven episodes: the rebuilding of Alexandria, Maggie's fight with the Reapers, and the introduction of the Commonwealth. It's been a lot to juggle, with the Commonwealth taking a bit of backseat as The Walking Dead season 11 works to establish the Reapers as a credible threat. Now, though, the Commonwealth's plot is picking up as more characters are introduced and the community is opening up.
The Commonwealth is being explored through the eyes of Eugene, Ezekiel, Yumiko, and Princess, who were first captured by their guards at the end of season 10 and have now been allowed entry. Since being processed, they've all been assigned jobs based on what their occupation was prior to the outbreak. Eugene, however, is more concerned with securing aid for Alexandria as that was the whole point of their journey, but Deputy Governor Lance Hornsby hasn't been very forthcoming about helping out. Frustrated and wanting to contact Alexandria, Eugene sneaks into the radio room, but doing so gets him along with Stephanie, Ezekiel, and Princess arrested. As punishment, they're forced to clear out walkers from an area the Commonwealth's wants to expand into, and it's here they meet Sebastian.
While Eugene, Stephanie, Ezekiel, and Princess are laboring in The Walking Dead season 11, episode 7 "Promises Broken," they see Sebastian and his girlfriend, Kayla, leaving for a picnic and accompanied by a security detail. Later on, after Eugene and Stephanie are reassigned to clear out a different section, they see Sebastian and Kayla again, but there's no security in sight. When some walkers get too close, Eugene and Stephanie step in and kill them before anyone is bitten. One would assume Sebastian would be grateful for the rescue, but instead, he's furious over his date being ruined. He berates them both, and when he calls Stephanie a "stupid b-tch," Eugene punches him. It's of course at this moment that the security detail reappears and arrests Eugene for attacking Sebastian since he is, after all, the son of Governor Pamela Milton, the Commonwealth's leader.
From this brief appearance alone, it's pretty obvious Sebastian is an entitled jerk who expects special treatment from everyone within the Commonwealth. Even Mercer, the stoic head of security, must fall in line with Sebastian's demands. Maintaining order in the Commonwealth is very much based on the established hierarchy, and as Sebastian is the son of Governor Pamela Milton, there isn't much anyone can do without causing a big disruption. The Commonwealth prides itself on being a safe, orderly community, and since many of the residents couldn't survive on the outside, there are few who are willing to shakes things up.
This is exactly how he acts in The Walking Dead comics, too, and his behavior doesn't sit well with Rick when he finally visits the Commonwealth. On more than one occasion, Sebastian's selfish behavior causes problems as Rick and Pamela try creating an alliance between their two communities. And while Pamela recognizes her son is far from perfect, she doesn't do much at all to discipline him. Instead, he's allowed to act as he pleases, and his smug outlook eventually results is one of The Walking Dead comic's most shocking and tragic moments. Presumably, the TV show plans to follow a similar route, though rather than Rick, it's seems it'll be Eugene who tries to knock some sense into him.
Sebastian's pompousness is especially irritating when it's taken within the context of The Walking Dead as a whole. For most people, life is a struggle every day, and to have someone acting like a spoiled rich kid comes in such stark contrast to their experiences. For that reason alone, Sebastian would easily be the most hated character in the whole series, but it's how his entitled behavior ends up nearly ruining everything that really earns him that title.