These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Community S2 E11: Abed's Uncontrollable Christmas
Designated Villain: Britta mostly, but Duncan too. Granted, he was trying to help Abed for his own purposes, but he was trying to help him. And what Abed was doing isn't healthy.
Duncan stops being "designated" about halfway through the episode, when his motivations switch from helping Abed so he can study his condition and possibly secure a publishing deal based on it (motives which are self-interested but more-or-less benevolent) to gaining revenge on Abed dredging up memories of his own unhappy Christmases, where he's clearly motivated by little more than spite.
Nonetheless, the episode can be quite uncomfortable regarding the whole thing, since the two people who realize that what Abed's doing is incredibly unhealthy and try to help him (even if it was selfishly in Duncan's case, and he stopped trying to help after having to be reminded of his own unhappy Christmas memories) are cast as the villains, with Britta being a Designated Villain until she learns to accept Abed's delusions.
The episode's last scene shows the group watching a Christmas special on TV. In the final shot, the screen on the set goes blank and we briefly see a reflection of the characters in live-action form, signifying that Abed's breakdown has finally ended.
The reason why Abed's searching for the true meaning of Christmas: Every year his mother would visit on December 9th to celebrate Christmas with him and watch Rudolph. This year, she didn't because she has a new family.
Abed's song about Britta when he leaves her behind:
Britta-Bot, Programmed badly, Wires with fraying ends. Functioning Mad and sadly. No faith in herself Or friends.
Any sympathy gained by it is pretty much negated by his Jerkass behavior at the end of the episode, but Duncan's outburst about his missing father and terrible home life counts.
One that doubles as Fridge Brilliance: Of course Pierce is the only one to stay 'til the end: this is his first Christmas without his mom, too.