Return to Angel Island is an arc in which following the year that Sonic was trapped in space and believed dead, Eggman went to war with Knothole and the Kingdom of Acorn, and Knuckles and the Chaotix had decided upon helping them as Angel Island had the Brotherhood.
Out of universe, the context was until M25YL, Ken had finished his “grand plan” for Knuckles following the beyond idiotic arc where he died saving Dimitri’s life, and going through echidna heaven. Since Ken was no longer writing plots about Knuckles and the echidnas, either due to being done, or editorial not wanting the stories anymore, this was the first time in years that Bollers was allowed to use the Angel Island crew.
Bollers - being a fan of the games - immediately hopped onto the chance to not only have the arc tie into his plans, but tie it far, far closer to the game lore. Knuckles - following Issue 125 where he came back to life and used his remaining Chaos Powers to help stop the doomsday device planted by a group of genocidal aliens (and what caused Sonic to be flung into space as he was trying to stop it, being the only one fast enough to do so).
Anyways, Knuckles had been depowered, and was ultimately feeling weaker due to it, getting a sense of inferiority about it. Then, he discovers what has happened to Angel Island. Eggman - being Eggman - finally decided to take off the kid gloves. Unleashing the full might of his empire onto the island, he easily destroys both the Brotherhood of Guardians (leaving them missing, thank god), and the Dark Legion. He razes Echidnapolis to the ground, and removes the echidna of all their technological advancements, enslaving them.
This has the result of bringing the echidnas back to their ancient depictions from Sonic Adventure, undertaking more traditional clothes like the Knuckles Tribe, and Bollers - calling out the ugly side of the chosen one legends - has the echidnas now believe Knuckles was a god like figure named the Avatar who was capable of destroying Eggman, and saving them all, which isn’t the case whatsoever due to his lacking powers, and weakening strength.
At the same time, the remains of the Dark Legion - led by the newly introduced Dr. Finitevus has picked up the slack, liberating echidnas where they can, and using their technological prowess to dismantle operations on the island. For once, we get an actual decent conflict where the Dark Legion is beyond pissed that their aid to the echidnas are ignored, because they’re too busy naively waiting for a god like Knuckles to save the day, when they’ve been doing their hardest to do so as is. It’s implied they have ulterior motives, but it also has a good reason for why they’d be pissed overall.
Then we get to Knuckles. The whole arc is essentially a call out of Ken’s boring writing, and a course correct to make things interesting. Due to his failing strength, Knuckles dons his SA2 power ups to help him get a boost. When they get to Angel Island, Echidnaopolis is destroyed, and the decades of constantly dicking over mobians because they believed themselves superior finally caught up to them (the Brotherhood at one point allowed Eggman to do as he pleased, essentially saying “lol, not our problem”, meaning this was well deserved. Even the hypocritical treatment of the Dingos bit them in the ass, as Eggman was able to convince them to work for him, due to being oppressed by the echidnas for so long.
Due to the destruction and enslavement, Angel Island under Bollers now resembled the game’s version properly, with several game zones appearing, the echidnas reverting back to the clothing and superstition of the Knuckles Clan, Knuckles’s brother having his ridiculously silly and long name (originally made by Penders) given a shorter pet name that was perfect (Bollers had given him the nickname of Kneecaps the Echidna).
Above all else, Knuckles is the star. After so many issues of being written as a boring shell of a character by Penders, Bollers had drained him of every ounce of overpowered ability, and brought him back to his personality from the games. He’s got self doubt issues due to the heavy legends being told about him, when he isn’t able to live up to the echidnas’ hype. His firery attitude is back is full force, with his hot temper, and sense of right and wrong finally brought back to the forefront. For all the arc’s achievements, finally making Knuckles be like Knuckles is topping the list. There is so much great comedy in this arc that comes off from Knuckles’ temper, and Sonic and the Chaotix teasing him, or vice versa.
He also finally gets to realise who the bad guys actually are. Knuckles at the end of Penders’ backups was a dumbass who was helping the Dark Legion after they pulled Angel Island into another dimension (Knuckles knew they did this), and his death was him saving Dimitri (the Legion’s leader). The first thing he does upon seeing them in this arc is charging right at them with fury, and Sonic pointing out how much Knuckles hates the legion. Knuckles is also beyond weirded out by the echidnas treating him like this god like figure, and constantly asks to be referred to by his name, not Avatar.
At the end of the arc, not only do they find the encaptured Locke, but Knuckles ends up finding power to dismantle the operation on Angel Island. Not his crappy Chaos Knuckles form, but rather he turns into Hyper Knuckles (in a homage to Mega Man Zero 2 no less), and uses the form and the help of Sonic and the Chaotix to save the echidnas from Eggman.
However, what you might be surprised to learn is prior to Ian, this is actually where the call outs of Locke and the Brotherhood starts. Upon being rescued, and the island liberated, Locke expected Knuckles to stick around and help find the Brotherhood, in which Knuckles says he can’t, because he’s helping with the war on Mobius, which leads to Knuckles finally standing up to his father and not backing down, calling Locke out on his selfishness for once.
I can’t really do justice to the arc with a quick description, but the short version of it all is that it’s an arc that actually makes stuff happen, has all of the echidnas terrible actions finally have consequences, tries to bring everything back to the games’ lore with the introduction of Hidden Palace, and a ton of other zones, make the Dark Legion interesting, and overall bring Knuckles back in line with his game counterpart.
And thus as you can imagine, Penders despised this. Everything I just mentioned, he loathed with a passion. He hated having his cast called out on their shit actions, he hated Angel Island and Echidnapolis being enslaved and razed, he hated Knuckles standing up to Locke, and hoo boy, does he have a grudge against Kneecaps the Echidna following the nickname.
Penders acts like a completely petty child in reference to this arc. Not only does he hate it, not only did he claim that Bollers had vindictively stolen and destroyed his work and lore (he likes to act like only he is entitled to use his characters, although that sure as fuck didn’t stop Penders using Mina and trying to utterly wreck her as a character), following Bollers getting ousted from the comic, and Penders becoming head lead (easily the darkest period of the comic) - he decided to only try to quickly retcon and revert things to normal (Echidnapolis was nearly rebuilt within a few issues, Locke tried to find the brotherhood), but he decided like the petty child he is to fuck around with Bollers’ intended plans.
First things first - there was Bollers’ planned arc with tackling Sally’s emotional baggage - Penders scrapped that, turned it into a bunch of love triangle melodrama, and made it beyond dreadful, and to this day, he still loves to tout around the idea that the Slap was a awful idea conceived by Bollers, and that Penders was somehow “fixing it” when he only made it much, MUCH worse.
Secondly, he essentially tried to character assassinate Mina. He makes a whole milestone story about Evil Sonic kidnapping and taking Sonic’s place on Mobius, which leads to him hitting on every girl he sees. This includes reverting Mina’s character development and making her nearly cheat on Ash, but also includes having Evil Sonic literally have sex with Bunnie and try to be disgustingly sly about it (and yes, given that Bunnie thought it was regular Sonic - there’s a LOT of horrific implications brought about by Penders doing that).
Thirdly and most infamously - Bollers had a plan that Antoine would be changed by the war and would eventually be corrupted by the source of all, Penders retroactively changed all this by claiming it was simply Evil Antoine all along, and made a contrived and boring plot where Sally and Evil Antoine get married because “”””drama””””. That may have been for the better, in fairness depending on who you ask, but still - it was done out of pettiness.
So yeah, Penders doesn’t like this arc very much, big surprise.