After escaping from Alexandria in The Walking Dead's midseason premiere, Negan visited the site where he brutally murdered Glenn and Abraham at the start of season 7. The former leader of the Saviors has been a prisoner of Alexandria for the past six years, locked up in a small cell as a symbol of civilization and justice for the people. However, after Gabriel accidentally left his cell door unlocked and Judith Grimes elected to look the other way at the wall, Negan enjoyed an entire episode of freedom in season 9, episode 9, "Adaptation."
After spending two seasons as The Walking Dead's main villain, Negan has since been supplanted by a chilling new threat: the Whisperers. This group of wandering killers survive by wearing the skins of walkers and moving with walker groups to protect themselves from both the living and the dead. In the midseason finale the Whisperers killed fan-favorite character Jesus, and there is surely more bloodshed on the way.
Negan is currently oblivious to all this, however, as he spent his time on the outside revisiting his past "glories." While he acquired a new leather jacket and spent a lot of time lurking around the ruins of the Sanctuary, the first stop on Negan's trip down memory lane was to the clearing where he first met the Alexandrians, and taught them a brutal lesson by killing off two main characters. Abraham and Glenn both met a grisly end after being beaten to death with Negan's precious bat, Lucille, and Glenn's death proved to be particularly controversial among fans - both because of how beloved the character was, and because of how gory his beating was. As you can see below, their killer returned to the scene of the crime in the midseason premiere.
The Walking Dead has clearly been setting up a redemption arc for Negan, starting with Carl's dream of the former villain one day becoming part of the community at Alexandria. Negan has been on a similar road to redemption in the comics, with Rick at one point reflecting on Negan's crimes by pointing out that he, too, has killed plenty of men who were probably people's husbands, and wondering if the two of them are really so different. However, one of the biggest barriers to fans of the TV show accepting Negan as a potential "good guy" is the still-fresh memory of what he did to Glenn and Abraham. Six years may have passed for the Alexandrians, but in the real world Negan was still a villain a mere ten episodes ago.
With all that in mind, the return to the clearing may have been intended as an assurance that the show hasn't forgotten Negan's crimes, and may also be a sign that Negan now regrets his earlier actions. During this scene he is symbolically brought to his knees, just like the Alexandrians were, and throws up violently after drinking creek water - a reminder of just how low Negan has been brought. His return to the Sanctuary also highlighted the fact that Negan really has lost everything, including his entire following of Saviors.
Negan is ultimately caught by Judith, but it appeared that he was already on his way back to Alexandria willingly, and he put up little resistance to being apprehended. His journey outside was surely a turning point for the character, and while he will surely be put back behind bars, it may not be much longer until he is freed. Maggie, the character who had the strongest hatred for Negan, is now out of the show, and with a war stirring between the Alexandrians and the Whisperers, our survivors may need all the help they can get.