Anti-Climax Boss: Clyde, the main antagonist of season 6 (at first), is taken down by the duo in practically two seconds.
Subverted in the season 6 finale, where he comes back to hold off Chief and Arbiter while the real Big Bad makes his escape. Despite doing a more efficient job in suppressing the two, he is unceremoniously taken down again, but it isn't shown until Chief watches a replay later on.
Eugene and his clan in season 7 end up being pushovers once Arbiter and Chief get the jump on them. Tyler and Colin are both fragged due to circumstances outside of the game, and Eugene kills himself out of spite.
Alas, Poor Scrappy: Different in the fact that they're already dead, but Cortana's last interactions with Chief as a ghost are essentially telling him that Tyler and Colin got what they deserved, Eugene's suicide was neither his fault nor Arbiter's and that he's changed enough for her to finally rest in peace, complete with a final request for him to be as much as a friend as he can to Arbiter in their final moments. Made even worse with Chief admitting that he does want to be friends with Cortana and realizing that he loves her...only for her to disappear before she can hear it.
Author's Saving Throw: Jon has confirmed that Season 8 will end on a happier note for the toys, and the preview shows them both alive and well, albeit with amnesia and trapped far away in the galaxy.
Broken Base: Between fans of the show who like that the show got darker and turned into more of a dramatic type of series and fans who prefer the lighter and comedic earlier episodes.
"Ignition", the season 7 finale, further divided the base because of how the toys die, and other factors.
Ensemble Darkhorse: Greg the spider has quite a few fans, to the point where they hope he returns for the next season. A completely different reception to what happened when Todd, Travis and Cortana were introduced.
On the comments of pretty much all the new videos, there is at least a few people who really want Greg to come back after disappearing in "Cheaters".
Kevin from Season 6 also seems to have quite a few fans.
Fridge Horror: Way back in Master Chief sucks at Halo 2, Chief attempts suicide over finding out that the Halo 3 Beta is over. We are supposed to find this funny, because it seemingly shows that he's taking things too seriously and obsessing way too much over a game. But when you think about it, he's a living action figure. When he says "my life is empty without Halo"? He means that completely sincerely. There really is nothing else in his life.
Fridge Logic: The reward for Scott's capture allowed them to stay in Canada.
Hate Sink: Adam is a satire of vulgar, immature and game addicted spoiled brats rolled into one 8 year old piece of scum, so of course he was meant to be hated by everybody in the show and the audience.
I Am Not Shazam: There are lots of examples of Chief referring to characters by the title of their games. In Beta he's disappointed because you can only play as 'Halo' (Spartans) now. In Hypermail, there's this exchange:
Chief: bitch plz / im teh halo mastar / u get down on ur fucking knees when u talk 2 meh about halo / go on / GET DOWN
Arbiter: Says the guy who thinks you still play as Master Chief in Reach.
Chief: who teh hell else w00d it b dipshit? metroid? hes from taht stuped gay cube gaem / w/e its called i dunno
Misaimed Fandom: A recent episode revolved around Chief criticising the Arbiter for wanting to play a PlayStation 3 game. Many fans thought it was supposed to be a Take That at the PS3 when it was supposed to be a Take That at the elitist 360 fanboys.
And if that wasn't enough, he fragged Claire just for the sake of it.
If you thought that was bad, he insulted a fellow racer for having a dead mother and said that her death just requires him to have extra lube when screwing her.
And if that REALLY wasn't enough, he declares that he has lost all respect for his mother - after she tries to make a last, desperate plea for him to start treating her like a human being - saying "No wonder Dad left you, you spineless fucking bitch". GOD.
Chief arguably crosses it when he accidentally kills Cortana
The fact Chaos Theosis can ban you by killing you once only, or even if you quit or turn your Xbox off. Their rampage at the end of Remission is just chilling.
Cortana's voice as she was melting. BRRRR.
Also the episode that Chief has while playing Oddball, flashing back to Cortana's murder. It's made all the worse by the fact that he is holding the oddball... which is a flaming skull.
The opening of "Descent". It features a Flash-forward depicting Chief, seemingly torn in half, lying motionless on the bathroom floor while Arbiter contemplates suicide by jumping out of the apartment window.
After killing Cortana, Chief starts seeing hallucinatory images of her all over the place, but this becomes Nightmare Fuel for the viewers in the latest episode, "Wake", in which Chief gets angry at the controller's faulty batteries, looks back up at the screen, and a GHOSTLY IMAGE OF CORTANAIS STARING STRAIGHT AT THE CAMERA. Time to change your underwear, viewers!
Eugene's final words after a long pause, followed by the gunshot, can be quite chilling.
Eugene: So long.
In "Ignition", Arbiter is so infuriated upon learning the truth about Cortana that he tears Chief apart into five pieces - the top piece, a limbless upper torso with Chief's visorless head, spouting gibberish endlessly in agony.
The shooting range scene in "Nervewreck", with Arbiter's vision of Eugene suddenly rushing towards the camera.
The Scrappy - Cortana, Travis and Todd were all scrappies but Cortana seems to get the most hate due to the fact she did nothing notable other than bitch about Chief being an idiot/sexist and bottom to Todd.
The new characters introduced in Arby 'n' the Chief in L.A. got quite a lot of hate at the time as well. Especially Sonic when he was first introduced.
Scrub: Arbiter believes that only cheap players use Martydom in Call of Duty, as well as pick Rocket Fight in Halo 3.
Greg. In his first appearance, he gets told by Arbiter that him and his species are repulsive, when he just wanted to hang out. Though thankfully Arbiter decides to befriend him afterwards. Chief constantly treats him like crap, which eventually ends up with Chief trying to kill Greg with a knife after Arbiter got Greg to lock him away so that he wouldn't crash the wedding, despite the fact that Greg felt horrible about it. He becomes self aware of his appearance when Arbiter decides not to play Scrabble with him one time, and then he hears what Arbiter said to Claire about how much Greg scares him. So he decides to leave.
Mrs. Mcintyre. Her husband left her some time before Season 6. She also has to put up with Adam, her son.
From season 5 and onwards, Arbiter himself becomes a pretty big woobie. His realisation that being a living toy means he will spend his entire life confined within a small apartment with only Chief to keep him company and that his life doesn't have any meaning or purpose slowly drives him into a depression. Especially since season 7 shows Chief and Arbiter deteriorating and breaking apart, having to tape and glue themselves back together really drives this home, to the point that Arbiter eventually agrees to finally partake in Eugene and his dangerous fragban software.